diff --git a/inc/peanut_gb.h b/inc/peanut_gb.h
index bff8c3a..0e13a08 100644
--- a/inc/peanut_gb.h
+++ b/inc/peanut_gb.h
@@ -1,7 +1,7 @@
 /**
  * MIT License
  *
- * Copyright (c) 2018 Mahyar Koshkouei
+ * Copyright (c) 2018-2022 Mahyar Koshkouei
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to
@@ -29,28 +29,87 @@
  * is Copyright (c) 2015-2019 Lior Halphon.
  */
 
-#pragma once
+#ifndef PEANUT_GB_H
+#define PEANUT_GB_H
 
-#include "hedley.h"
+#if defined(__has_include)
+# if __has_include("version.all")
+#  include "version.all"	/* Version information */
+# endif
+#else
+/* Stub __has_include for later. */
+# define __has_include(x) 0
+#endif
 
+#include <stdlib.h>	/* Required for qsort and abort */
 #include <stdint.h>	/* Required for int types */
 #include <string.h>	/* Required for memset */
 #include <time.h>	/* Required for tm struct */
 
+/**
+* If PEANUT_GB_IS_LITTLE_ENDIAN is positive, then Peanut-GB will be configured
+* for a little endian platform. If 0, then big endian.
+*/
+#if !defined(PEANUT_GB_IS_LITTLE_ENDIAN)
+/* If endian is not defined, then attempt to detect it. */
+# if defined(__BYTE_ORDER__)
+#  if __BYTE_ORDER__ != __ORDER_LITTLE_ENDIAN__
+/* Building for a big endian platform. */
+#   define PEANUT_GB_IS_LITTLE_ENDIAN 0
+#  else
+#   define PEANUT_GB_IS_LITTLE_ENDIAN 1
+#  endif /* __BYTE_ORDER__ != __ORDER_LITTLE_ENDIAN__ */
+# elif defined(_WIN32)
+/* We assume that Windows is always little endian by default. */
+#  define PEANUT_GB_IS_LITTLE_ENDIAN 1
+# elif !defined(PEANUT_GB_IS_LITTLE_ENDIAN)
+#  error "Could not detect target platform endian. Please define PEANUT_GB_IS_LITTLE_ENDIAN"
+# endif
+#endif /* !defined(PEANUT_GB_IS_LITTLE_ENDIAN) */
+
+#if PEANUT_GB_IS_LITTLE_ENDIAN == 0
+# error "Peanut-GB only supports little endian targets"
+/* This is because the logic has been written with assumption of little
+ * endian byte order. */
+#endif
+
+/** Definitions for compile-time setting of features. **/
 /**
  * Sound support must be provided by an external library. When audio_read() and
  * audio_write() functions are provided, define ENABLE_SOUND to a non-zero value
  * before including peanut_gb.h in order for these functions to be used.
  */
 #ifndef ENABLE_SOUND
-#	define ENABLE_SOUND 0
+# define ENABLE_SOUND 0
 #endif
 
 /* Enable LCD drawing. On by default. May be turned off for testing purposes. */
 #ifndef ENABLE_LCD
-#	define ENABLE_LCD 1
+# define ENABLE_LCD 1
 #endif
 
+/* Adds more code to improve LCD rendering accuracy. */
+#ifndef PEANUT_GB_HIGH_LCD_ACCURACY
+# define PEANUT_GB_HIGH_LCD_ACCURACY 1
+#endif
+
+/* Play BIOS before playing cartridge.
+ * This setting is currently not implemented. */
+#ifndef PEANUT_GB_USE_BIOS
+# define PEANUT_GB_USE_BIOS 0
+#endif
+
+/* Use intrinsic functions. This may produce smaller and faster code. */
+#ifndef PEANUT_GB_USE_INTRINSICS
+# define PEANUT_GB_USE_INTRINSICS 1
+#endif
+
+/* Function definition for abort(). */
+#ifndef PEANUT_GB_ABORT
+# define PEANUT_GB_ABORT() abort()
+#endif
+
+/** Internal source code. **/
 /* Interrupt masks */
 #define VBLANK_INTR	0x01
 #define LCDC_INTR	0x02
@@ -62,7 +121,7 @@
 /* Memory section sizes for DMG */
 #define WRAM_SIZE	0x2000
 #define VRAM_SIZE	0x2000
-#define HRAM_SIZE	0x0100
+#define HRAM_IO_SIZE	0x0100
 #define OAM_SIZE	0x00A0
 
 /* Memory addresses */
@@ -91,16 +150,16 @@
 
 /* Serial clock locked to 8192Hz on DMG.
  * 4194304 / (8192 / 8) = 4096 clock cycles for sending 1 byte. */
-#define SERIAL_CYCLES		4096
+#define SERIAL_CYCLES       4096
 
 /* Calculating VSYNC. */
-#define DMG_CLOCK_FREQ		4194304.0
-#define SCREEN_REFRESH_CYCLES	70224.0
-#define VERTICAL_SYNC		(DMG_CLOCK_FREQ/SCREEN_REFRESH_CYCLES)
+#define DMG_CLOCK_FREQ      4194304.0
+#define SCREEN_REFRESH_CYCLES 70224.0
+#define VERTICAL_SYNC       (DMG_CLOCK_FREQ/SCREEN_REFRESH_CYCLES)
 
 /* SERIAL SC register masks. */
-#define SERIAL_SC_TX_START	0x80
-#define SERIAL_SC_CLOCK_SRC	0x01
+#define SERIAL_SC_TX_START  0x80
+#define SERIAL_SC_CLOCK_SRC 0x01
 
 /* STAT register masks */
 #define STAT_LYC_INTR       0x40
@@ -155,67 +214,188 @@
 
 #define ROM_HEADER_CHECKSUM_LOC	0x014D
 
+/* Local macros. */
 #ifndef MIN
-	#define MIN(a, b)   ((a) < (b) ? (a) : (b))
+# define MIN(a, b)          ((a) < (b) ? (a) : (b))
+#endif
+
+#define PEANUT_GB_ARRAYSIZE(array)    (sizeof(array)/sizeof(array[0]))
+
+#if !defined(__has_builtin)
+/* Stub __has_builtin if it isn't available. */
+# define __has_builtin(x) 0
+#endif
+
+#if __has_builtin(__builtin_unreachable)
+# define PGB_UNREACHABLE() __builtin_unreachable()
+#else
+# define PGB_UNREACHABLE() PEANUT_GB_ABORT()
+#endif
+
+#if PEANUT_GB_USE_INTRINSICS
+/* If using MSVC, only enable intrinsics for x86 platforms*/
+# if defined(_MSC_VER) && __has_include("intrin.h") && \
+	(defined(_M_IX86_FP) || defined(_M_AMD64) || defined(_M_X64))
+/* Define instrinsic functions for MSVC. */
+#  include <intrin.h>
+#  define PGB_INTRIN_SBC(x,y,cin,res) _subborrow_u8(cin,x,y,&res)
+#  define PGB_INTRIN_ADC(x,y,cin,res) _addcarry_u8(cin,x,y,&res)
+# endif /* MSVC */
+
+/* Check for instrinsic functions in GCC and Clang. */
+# if __has_builtin(__builtin_sub_overflow)
+#  define PGB_INTRIN_SBC(x,y,cin,res) __builtin_sub_overflow(x,y+cin,&res)
+#  define PGB_INTRIN_ADC(x,y,cin,res) __builtin_add_overflow(x,y+cin,&res)
+# endif
+#endif /* PEANUT_GB_USE_INTRINSICS */
+
+#if defined(PGB_INTRIN_SBC)
+# define PGB_INSTR_SBC_R8(r,cin)						\
+	{									\
+		uint8_t temp;							\
+		gb->cpu_reg.f_bits.c = PGB_INTRIN_SBC(gb->cpu_reg.a,r,cin,temp);\
+		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.a ^ r ^ temp) & 0x10) > 0;	\
+		gb->cpu_reg.f_bits.n = 1;					\
+		gb->cpu_reg.f_bits.z = (temp == 0x00);				\
+		gb->cpu_reg.a = temp;						\
+	}
+
+# define PGB_INSTR_CP_R8(r)							\
+	{									\
+		uint8_t temp;							\
+		gb->cpu_reg.f_bits.c = PGB_INTRIN_SBC(gb->cpu_reg.a,r,0,temp);	\
+		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.a ^ r ^ temp) & 0x10) > 0;	\
+		gb->cpu_reg.f_bits.n = 1;					\
+		gb->cpu_reg.f_bits.z = (temp == 0x00);				\
+	}
+#else
+# define PGB_INSTR_SBC_R8(r,cin)						\
+	{									\
+		uint16_t temp = gb->cpu_reg.a - (r + cin);			\
+		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;			\
+		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.a ^ r ^ temp) & 0x10) > 0; \
+		gb->cpu_reg.f_bits.n = 1;					\
+		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);			\
+		gb->cpu_reg.a = (temp & 0xFF);					\
+	}
+
+# define PGB_INSTR_CP_R8(r)							\
+	{									\
+		uint16_t temp = gb->cpu_reg.a - r;				\
+		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;			\
+		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.a ^ r ^ temp) & 0x10) > 0; \
+		gb->cpu_reg.f_bits.n = 1;					\
+		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);			\
+	}
+#endif  /* PGB_INTRIN_SBC */
+
+#if defined(PGB_INTRIN_ADC)
+# define PGB_INSTR_ADC_R8(r,cin)						\
+	{									\
+		uint8_t temp;							\
+		gb->cpu_reg.f_bits.c = PGB_INTRIN_ADC(gb->cpu_reg.a,r,cin,temp);\
+		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.a ^ r ^ temp) & 0x10) > 0; \
+		gb->cpu_reg.f_bits.n = 0;					\
+		gb->cpu_reg.f_bits.z = (temp == 0x00);				\
+		gb->cpu_reg.a = temp;						\
+	}
+#else
+# define PGB_INSTR_ADC_R8(r,cin)						\
+	{									\
+		uint16_t temp = gb->cpu_reg.a + r + cin;			\
+		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;			\
+		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.a ^ r ^ temp) & 0x10) > 0; \
+		gb->cpu_reg.f_bits.n = 0;					\
+		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);			\
+		gb->cpu_reg.a = (temp & 0xFF);					\
+	}
+#endif /* PGB_INTRIN_ADC */
+
+#define PGB_INSTR_DEC_R8(r)							\
+	r--;									\
+	gb->cpu_reg.f_bits.h = ((r & 0x0F) == 0x0F);				\
+	gb->cpu_reg.f_bits.n = 1;						\
+	gb->cpu_reg.f_bits.z = (r == 0x00);
+	
+
+#if PEANUT_GB_IS_LITTLE_ENDIAN
+# define PEANUT_GB_GET_LSB16(x) (x & 0xFF)
+# define PEANUT_GB_GET_MSB16(x) (x >> 8)
+# define PEANUT_GB_GET_MSN16(x) (x >> 12)
+# define PEANUT_GB_U8_TO_U16(h,l) ((l) | ((h) << 8))
+#else
+# define PEANUT_GB_GET_LSB16(x) (x >> 8)
+# define PEANUT_GB_GET_MSB16(x) (x & 0xFF)
+# define PEANUT_GB_GET_MSN16(x) ((x & 0xF0) >> 4)
+# define PEANUT_GB_U8_TO_U16(h,l) ((h) | ((l) << 8))
 #endif
 
 struct cpu_registers_s
 {
-	/* Combine A and F registers. */
-	union
+/* Change register order if big endian.
+ * Macro receives registers in little endian order. */
+#if PEANUT_GB_IS_LITTLE_ENDIAN
+# define PEANUT_GB_LE_REG(x,y) x,y
+#else
+# define PEANUT_GB_LE_REG(x,y) y,x
+#endif
+	/* Define specific bits of Flag register. */
+	struct
 	{
-		struct
-		{
-			/* Define specific bits of Flag register. */
-			union
-			{
-				struct
-				{
-					unsigned unused : 4;
-					unsigned c : 1; /* Carry flag. */
-					unsigned h : 1; /* Half carry flag. */
-					unsigned n : 1; /* Add/sub flag. */
-					unsigned z : 1; /* Zero flag. */
-				} f_bits;
-				uint8_t f;
-			};
-			uint8_t a;
-		};
-		uint16_t af;
-	};
+		unsigned c : 1; /* Carry flag. */
+		unsigned h : 1; /* Half carry flag. */
+		unsigned n : 1; /* Add/sub flag. */
+		unsigned z : 1; /* Zero flag. */
+	} f_bits;
+	uint8_t a;
 
 	union
 	{
 		struct
 		{
-			uint8_t c;
-			uint8_t b;
-		};
-		uint16_t bc;
-	};
+			uint8_t PEANUT_GB_LE_REG(c,b);
+		} bytes;
+		uint16_t reg;
+	} bc;
 
 	union
 	{
 		struct
 		{
-			uint8_t e;
-			uint8_t d;
-		};
-		uint16_t de;
-	};
+			uint8_t PEANUT_GB_LE_REG(e,d);
+		} bytes;
+		uint16_t reg;
+	} de;
 
 	union
 	{
 		struct
 		{
-			uint8_t l;
-			uint8_t h;
-		};
-		uint16_t hl;
-	};
+			uint8_t PEANUT_GB_LE_REG(l,h);
+		} bytes;
+		uint16_t reg;
+	} hl;
 
-	uint16_t sp; /* Stack pointer */
-	uint16_t pc; /* Program counter */
+	/* Stack pointer */
+	union
+	{
+		struct
+		{
+			uint8_t PEANUT_GB_LE_REG(p, s);
+		} bytes;
+		uint16_t reg;
+	} sp;
+
+	/* Program counter */
+	union
+	{
+		struct
+		{
+			uint8_t PEANUT_GB_LE_REG(c, p);
+		} bytes;
+		uint16_t reg;
+	} pc;
+#undef PEANUT_GB_LE_REG
 };
 
 struct count_s
@@ -226,49 +406,38 @@ struct count_s
 	uint_fast16_t serial_count;	/* Serial Counter */
 };
 
-struct gb_registers_s
-{
-	/* TODO: Sort variables in address order. */
-	/* Timing */
-	uint8_t TIMA, TMA, DIV;
-	union
-	{
-		struct
-		{
-			unsigned tac_rate : 2;	/* Input clock select */
-			unsigned tac_enable : 1;	/* Timer enable */
-			unsigned unused : 5;
-		};
-		uint8_t TAC;
-	};
+#define IO_JOYP	0x00
+#define IO_SB	0x01
+#define IO_SC	0x02
+#define IO_DIV	0x04
+#define IO_TIMA	0x05
+#define IO_TMA	0x06
+#define IO_TAC	0x07
+#define IO_IF	0x0F
+#define IO_BOOT	0x50
+#define IO_LCDC	0x40
+#define IO_STAT	0x41
+#define IO_SCY	0x42
+#define IO_SCX	0x43
+#define IO_LY	0x44
+#define IO_LYC	0x45
+#define	IO_DMA	0x46
+#define	IO_BGP	0x47
+#define	IO_OBP0	0x48
+#define IO_OBP1	0x49
+#define IO_WY	0x4A
+#define IO_WX	0x4B
+#define IO_IE	0xFF
 
-	/* LCD */
-	uint8_t LCDC;
-	uint8_t STAT;
-	uint8_t SCY;
-	uint8_t SCX;
-	uint8_t LY;
-	uint8_t LYC;
-	uint8_t DMA;
-	uint8_t BGP;
-	uint8_t OBP0;
-	uint8_t OBP1;
-	uint8_t WY;
-	uint8_t WX;
+#define IO_TAC_RATE_MASK	0x3
+#define IO_TAC_ENABLE_MASK	0x4
 
-	/* Joypad info. */
-	uint8_t P1;
-
-	/* Serial data. */
-	uint8_t SB;
-	uint8_t SC;
-
-	/* Interrupt flag. */
-	uint8_t IF;
-
-	/* Interrupt enable. */
-	uint8_t IE;
-};
+/* LCD Mode defines. */
+#define IO_STAT_MODE_HBLANK		0
+#define IO_STAT_MODE_VBLANK		1
+#define IO_STAT_MODE_SEARCH_OAM		2
+#define IO_STAT_MODE_SEARCH_TRANSFER	3
+#define IO_STAT_MODE_VBLANK_OR_TRANSFER_MASK 0x1
 
 #if ENABLE_LCD
 	/* Bit mask for the shade of pixel to display */
@@ -294,10 +463,11 @@ struct gb_registers_s
  */
 enum gb_error_e
 {
-	GB_UNKNOWN_ERROR,
+	GB_UNKNOWN_ERROR = 0,
 	GB_INVALID_OPCODE,
 	GB_INVALID_READ,
 	GB_INVALID_WRITE,
+	GB_HALT_FOREVER,
 
 	GB_INVALID_MAX
 };
@@ -307,7 +477,7 @@ enum gb_error_e
  */
 enum gb_init_error_e
 {
-	GB_INIT_NO_ERROR,
+	GB_INIT_NO_ERROR = 0,
 	GB_INIT_CARTRIDGE_UNSUPPORTED,
 	GB_INIT_INVALID_CHECKSUM
 };
@@ -362,9 +532,9 @@ struct gb_s
 	 *
 	 * \param gb_s			emulator context
 	 * \param gb_error_e	error code
-	 * \param val			arbitrary value related to error
+	 * \param addr			address of where error occured
 	 */
-	void (*gb_error)(struct gb_s*, const enum gb_error_e, const uint16_t val);
+	void (*gb_error)(struct gb_s*, const enum gb_error_e, const uint16_t addr);
 
 	/* Transmit one byte and return the received byte. */
 	void (*gb_serial_tx)(struct gb_s*, const uint8_t tx);
@@ -374,20 +544,17 @@ struct gb_s
 	{
 		unsigned gb_halt	: 1;
 		unsigned gb_ime		: 1;
+#if PEANUT_GB_USE_BIOS
 		unsigned gb_bios_enable : 1;
+#endif
 		unsigned gb_frame	: 1; /* New frame drawn. */
 
-#		define LCD_HBLANK	0
-#		define LCD_VBLANK	1
-#		define LCD_SEARCH_OAM	2
-#		define LCD_TRANSFER	3
-		unsigned lcd_mode	: 2;
 		unsigned lcd_blank	: 1;
 	};
 
 	/* Cartridge information:
 	 * Memory Bank Controller (MBC) type. */
-	uint8_t mbc;
+	int8_t mbc;
 	/* Whether the MBC has internal RAM. */
 	uint8_t cart_ram;
 	/* Number of ROM banks in cartridge. */
@@ -415,14 +582,14 @@ struct gb_s
 	};
 
 	struct cpu_registers_s cpu_reg;
-	struct gb_registers_s gb_reg;
+	//struct gb_registers_s gb_reg;
 	struct count_s counter;
 
 	/* TODO: Allow implementation to allocate WRAM, VRAM and Frame Buffer. */
 	uint8_t wram[WRAM_SIZE];
 	uint8_t vram[VRAM_SIZE];
-	uint8_t hram[HRAM_SIZE];
 	uint8_t oam[OAM_SIZE];
+	uint8_t hram_io[HRAM_IO_SIZE];
 
 	struct
 	{
@@ -480,80 +647,30 @@ struct gb_s
 		{
 			struct
 			{
-				unsigned a		: 1;
-				unsigned b		: 1;
+				unsigned a	: 1;
+				unsigned b	: 1;
 				unsigned select	: 1;
 				unsigned start	: 1;
 				unsigned right	: 1;
 				unsigned left	: 1;
-				unsigned up		: 1;
+				unsigned up	: 1;
 				unsigned down	: 1;
 			} joypad_bits;
 			uint8_t joypad;
 		};
 
-		unsigned ended : 1;
-
 		/* Implementation defined data. Set to NULL if not required. */
 		void *priv;
 	} direct;
 };
 
-/**
- * Tick the internal RTC by one second.
- * This was taken from SameBoy, which is released under MIT Licence.
- */
-void gb_tick_rtc(struct gb_s *gb)
-{
-	/* is timer running? */
-	if((gb->cart_rtc[4] & 0x40) == 0)
-	{
-		if(++gb->rtc_bits.sec == 60)
-		{
-			gb->rtc_bits.sec = 0;
-
-			if(++gb->rtc_bits.min == 60)
-			{
-				gb->rtc_bits.min = 0;
-
-				if(++gb->rtc_bits.hour == 24)
-				{
-					gb->rtc_bits.hour = 0;
-
-					if(++gb->rtc_bits.yday == 0)
-					{
-						if(gb->rtc_bits.high & 1)  /* Bit 8 of days*/
-						{
-							gb->rtc_bits.high |= 0x80; /* Overflow bit */
-						}
-
-						gb->rtc_bits.high ^= 1;
-					}
-				}
-			}
-		}
-	}
-}
-
-/**
- * Set initial values in RTC.
- * Should be called after gb_init().
- */
-void gb_set_rtc(struct gb_s *gb, const struct tm * const time)
-{
-	gb->cart_rtc[0] = time->tm_sec;
-	gb->cart_rtc[1] = time->tm_min;
-	gb->cart_rtc[2] = time->tm_hour;
-	gb->cart_rtc[3] = time->tm_yday & 0xFF; /* Low 8 bits of day counter. */
-	gb->cart_rtc[4] = time->tm_yday >> 8; /* High 1 bit of day counter. */
-}
-
 /**
  * Internal function used to read bytes.
+ * addr is host platform endian.
  */
-uint8_t __gb_read(struct gb_s *gb, const uint_fast16_t addr)
+uint8_t __gb_read(struct gb_s *gb, const uint16_t addr)
 {
-	switch(addr >> 12)
+	switch(PEANUT_GB_GET_MSN16(addr))
 	{
 	case 0x0:
 
@@ -611,106 +728,39 @@ uint8_t __gb_read(struct gb_s *gb, const uint_fast16_t addr)
 		if(addr < UNUSED_ADDR)
 			return gb->oam[addr - OAM_ADDR];
 
-		/* Unusable memory area. Reading from this area returns 0.*/
+		/* Unusable memory area. Reading from this area returns 0xFF.*/
 		if(addr < IO_ADDR)
 			return 0xFF;
 
-		/* HRAM */
-		if(HRAM_ADDR <= addr && addr < INTR_EN_ADDR)
-			return gb->hram[addr - HRAM_ADDR];
-
+		/* APU registers. */
 		if((addr >= 0xFF10) && (addr <= 0xFF3F))
 		{
 #if ENABLE_SOUND
 			return audio_read(addr);
 #else
-			return 1;
+			static const uint8_t ortab[] = {
+				0x80, 0x3f, 0x00, 0xff, 0xbf,
+				0xff, 0x3f, 0x00, 0xff, 0xbf,
+				0x7f, 0xff, 0x9f, 0xff, 0xbf,
+				0xff, 0xff, 0x00, 0x00, 0xbf,
+				0x00, 0x00, 0x70,
+				0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+				0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+				0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+			};
+			return gb->hram_io[addr - IO_ADDR] | ortab[addr - IO_ADDR];
 #endif
 		}
 
-		/* IO and Interrupts. */
-		switch(addr & 0xFF)
-		{
-		/* IO Registers */
-		case 0x00:
-			return 0xC0 | gb->gb_reg.P1;
-
-		case 0x01:
-			return gb->gb_reg.SB;
-
-		case 0x02:
-			return gb->gb_reg.SC;
-
-		/* Timer Registers */
-		case 0x04:
-			return gb->gb_reg.DIV;
-
-		case 0x05:
-			return gb->gb_reg.TIMA;
-
-		case 0x06:
-			return gb->gb_reg.TMA;
-
-		case 0x07:
-			return gb->gb_reg.TAC;
-
-		/* Interrupt Flag Register */
-		case 0x0F:
-			return gb->gb_reg.IF;
-
-		/* LCD Registers */
-		case 0x40:
-			return gb->gb_reg.LCDC;
-
-		case 0x41:
-			return (gb->gb_reg.STAT & STAT_USER_BITS) |
-			       (gb->gb_reg.LCDC & LCDC_ENABLE ? gb->lcd_mode : LCD_VBLANK);
-
-		case 0x42:
-			return gb->gb_reg.SCY;
-
-		case 0x43:
-			return gb->gb_reg.SCX;
-
-		case 0x44:
-			return gb->gb_reg.LY;
-
-		case 0x45:
-			return gb->gb_reg.LYC;
-
-		/* DMA Register */
-		case 0x46:
-			return gb->gb_reg.DMA;
-
-		/* DMG Palette Registers */
-		case 0x47:
-			return gb->gb_reg.BGP;
-
-		case 0x48:
-			return gb->gb_reg.OBP0;
-
-		case 0x49:
-			return gb->gb_reg.OBP1;
-
-		/* Window Position Registers */
-		case 0x4A:
-			return gb->gb_reg.WY;
-
-		case 0x4B:
-			return gb->gb_reg.WX;
-
-		/* Interrupt Enable Register */
-		case 0xFF:
-			return gb->gb_reg.IE;
-
-		/* Unused registers return 1 */
-		default:
-			return 0xFF;
-		}
+		/* HRAM */
+		if(addr >= IO_ADDR)
+			return gb->hram_io[addr - IO_ADDR];
 	}
 
+
+	/* Return address that caused read error. */
 	(gb->gb_error)(gb, GB_INVALID_READ, addr);
-	return 0xFF;
+	PGB_UNREACHABLE();
 }
 
 /**
@@ -718,7 +768,7 @@ uint8_t __gb_read(struct gb_s *gb, const uint_fast16_t addr)
  */
 void __gb_write(struct gb_s *gb, const uint_fast16_t addr, const uint8_t val)
 {
-	switch(addr >> 12)
+	switch(PEANUT_GB_GET_MSN16(addr))
 	{
 	case 0x0:
 	case 0x1:
@@ -843,7 +893,7 @@ void __gb_write(struct gb_s *gb, const uint_fast16_t addr, const uint8_t val)
 
 		if(HRAM_ADDR <= addr && addr < INTR_EN_ADDR)
 		{
-			gb->hram[addr - HRAM_ADDR] = val;
+			gb->hram_io[addr - IO_ADDR] = val;
 			return;
 		}
 
@@ -851,168 +901,179 @@ void __gb_write(struct gb_s *gb, const uint_fast16_t addr, const uint8_t val)
 		{
 #if ENABLE_SOUND
 			audio_write(addr, val);
+#else
+			gb->hram_io[addr - IO_ADDR] = val;
 #endif
 			return;
 		}
 
 		/* IO and Interrupts. */
-		switch(addr & 0xFF)
+		switch(PEANUT_GB_GET_LSB16(addr))
 		{
 		/* Joypad */
 		case 0x00:
 			/* Only bits 5 and 4 are R/W.
 			 * The lower bits are overwritten later, and the two most
 			 * significant bits are unused. */
-			gb->gb_reg.P1 = val;
+			gb->hram_io[IO_JOYP] = val;
 
 			/* Direction keys selected */
-			if((gb->gb_reg.P1 & 0b010000) == 0)
-				gb->gb_reg.P1 |= (gb->direct.joypad >> 4);
+			if((gb->hram_io[IO_JOYP] & 0b010000) == 0)
+				gb->hram_io[IO_JOYP] |= (gb->direct.joypad >> 4);
 			/* Button keys selected */
 			else
-				gb->gb_reg.P1 |= (gb->direct.joypad & 0x0F);
+				gb->hram_io[IO_JOYP] |= (gb->direct.joypad & 0x0F);
 
 			return;
 
 		/* Serial */
 		case 0x01:
-			gb->gb_reg.SB = val;
+			gb->hram_io[IO_SB] = val;
 			return;
 
 		case 0x02:
-			gb->gb_reg.SC = val;
+			gb->hram_io[IO_SC] = val;
 			return;
 
 		/* Timer Registers */
 		case 0x04:
-			gb->gb_reg.DIV = 0x00;
+			gb->hram_io[IO_DIV] = 0x00;
 			return;
 
 		case 0x05:
-			gb->gb_reg.TIMA = val;
+			gb->hram_io[IO_TIMA] = val;
 			return;
 
 		case 0x06:
-			gb->gb_reg.TMA = val;
+			gb->hram_io[IO_TMA] = val;
 			return;
 
 		case 0x07:
-			gb->gb_reg.TAC = val;
+			gb->hram_io[IO_TAC] = val;
 			return;
 
 		/* Interrupt Flag Register */
 		case 0x0F:
-			gb->gb_reg.IF = (val | 0b11100000);
+			gb->hram_io[IO_IF] = (val | 0b11100000);
 			return;
 
 		/* LCD Registers */
 		case 0x40:
-			if(((gb->gb_reg.LCDC & LCDC_ENABLE) == 0) &&
+			if(((gb->hram_io[IO_LCDC] & LCDC_ENABLE) == 0) &&
 				(val & LCDC_ENABLE))
 			{
 				gb->counter.lcd_count = 0;
 				gb->lcd_blank = 1;
 			}
 
-			gb->gb_reg.LCDC = val;
+			gb->hram_io[IO_LCDC] = val;
 
 			/* LY fixed to 0 when LCD turned off. */
-			if((gb->gb_reg.LCDC & LCDC_ENABLE) == 0)
+			if((gb->hram_io[IO_LCDC] & LCDC_ENABLE) == 0)
 			{
 				/* Do not turn off LCD outside of VBLANK. This may
 				 * happen due to poor timing in this emulator. */
-				if(gb->lcd_mode != LCD_VBLANK)
+				if((gb->hram_io[IO_STAT] & STAT_MODE) != IO_STAT_MODE_VBLANK)
 				{
-					gb->gb_reg.LCDC |= LCDC_ENABLE;
+					gb->hram_io[IO_LCDC] |= LCDC_ENABLE;
 					return;
 				}
 
-				gb->gb_reg.STAT = (gb->gb_reg.STAT & ~0x03) | LCD_VBLANK;
-				gb->gb_reg.LY = 0;
+				gb->hram_io[IO_STAT] = (gb->hram_io[IO_STAT] & ~0x03) | 1;
+				gb->hram_io[IO_LY] = 0;
 				gb->counter.lcd_count = 0;
 			}
 
 			return;
 
 		case 0x41:
-			gb->gb_reg.STAT = (val & 0b01111000);
+			gb->hram_io[IO_STAT] = (val & STAT_USER_BITS) | (gb->hram_io[IO_STAT] & STAT_MODE);
 			return;
 
 		case 0x42:
-			gb->gb_reg.SCY = val;
+			gb->hram_io[IO_SCY] = val;
 			return;
 
 		case 0x43:
-			gb->gb_reg.SCX = val;
+			gb->hram_io[IO_SCX] = val;
 			return;
 
 		/* LY (0xFF44) is read only. */
 		case 0x45:
-			gb->gb_reg.LYC = val;
+			gb->hram_io[IO_LYC] = val;
 			return;
 
 		/* DMA Register */
 		case 0x46:
-			gb->gb_reg.DMA = (val % 0xF1);
+		{
+			uint16_t dma_addr = (uint_fast16_t)val << 8;
+			gb->hram_io[IO_DMA] = val;
 
-			for(uint8_t i = 0; i < OAM_SIZE; i++)
-				gb->oam[i] = __gb_read(gb, (gb->gb_reg.DMA << 8) + i);
+			for(uint16_t i = 0; i < OAM_SIZE; i++)
+			{
+				gb->oam[i] = __gb_read(gb, dma_addr + i);
+			}
 
 			return;
+		}
 
 		/* DMG Palette Registers */
 		case 0x47:
-			gb->gb_reg.BGP = val;
-			gb->display.bg_palette[0] = (gb->gb_reg.BGP & 0x03);
-			gb->display.bg_palette[1] = (gb->gb_reg.BGP >> 2) & 0x03;
-			gb->display.bg_palette[2] = (gb->gb_reg.BGP >> 4) & 0x03;
-			gb->display.bg_palette[3] = (gb->gb_reg.BGP >> 6) & 0x03;
+			gb->hram_io[IO_BGP] = val;
+			gb->display.bg_palette[0] = (gb->hram_io[IO_BGP] & 0x03);
+			gb->display.bg_palette[1] = (gb->hram_io[IO_BGP] >> 2) & 0x03;
+			gb->display.bg_palette[2] = (gb->hram_io[IO_BGP] >> 4) & 0x03;
+			gb->display.bg_palette[3] = (gb->hram_io[IO_BGP] >> 6) & 0x03;
 			return;
 
 		case 0x48:
-			gb->gb_reg.OBP0 = val;
-			gb->display.sp_palette[0] = (gb->gb_reg.OBP0 & 0x03);
-			gb->display.sp_palette[1] = (gb->gb_reg.OBP0 >> 2) & 0x03;
-			gb->display.sp_palette[2] = (gb->gb_reg.OBP0 >> 4) & 0x03;
-			gb->display.sp_palette[3] = (gb->gb_reg.OBP0 >> 6) & 0x03;
+			gb->hram_io[IO_OBP0] = val;
+			gb->display.sp_palette[0] = (gb->hram_io[IO_OBP0] & 0x03);
+			gb->display.sp_palette[1] = (gb->hram_io[IO_OBP0] >> 2) & 0x03;
+			gb->display.sp_palette[2] = (gb->hram_io[IO_OBP0] >> 4) & 0x03;
+			gb->display.sp_palette[3] = (gb->hram_io[IO_OBP0] >> 6) & 0x03;
 			return;
 
 		case 0x49:
-			gb->gb_reg.OBP1 = val;
-			gb->display.sp_palette[4] = (gb->gb_reg.OBP1 & 0x03);
-			gb->display.sp_palette[5] = (gb->gb_reg.OBP1 >> 2) & 0x03;
-			gb->display.sp_palette[6] = (gb->gb_reg.OBP1 >> 4) & 0x03;
-			gb->display.sp_palette[7] = (gb->gb_reg.OBP1 >> 6) & 0x03;
+			gb->hram_io[IO_OBP1] = val;
+			gb->display.sp_palette[4] = (gb->hram_io[IO_OBP1] & 0x03);
+			gb->display.sp_palette[5] = (gb->hram_io[IO_OBP1] >> 2) & 0x03;
+			gb->display.sp_palette[6] = (gb->hram_io[IO_OBP1] >> 4) & 0x03;
+			gb->display.sp_palette[7] = (gb->hram_io[IO_OBP1] >> 6) & 0x03;
 			return;
 
 		/* Window Position Registers */
 		case 0x4A:
-			gb->gb_reg.WY = val;
+			gb->hram_io[IO_WY] = val;
 			return;
 
 		case 0x4B:
-			gb->gb_reg.WX = val;
+			gb->hram_io[IO_WX] = val;
 			return;
 
 		/* Turn off boot ROM */
 		case 0x50:
+#if PEANUT_GB_USE_BIOS
 			gb->gb_bios_enable = 0;
+#endif
 			return;
 
 		/* Interrupt Enable Register */
 		case 0xFF:
-			gb->gb_reg.IE = val;
+			gb->hram_io[IO_IE] = val;
 			return;
 		}
 	}
 
+	/* Return address that caused write error. */
 	(gb->gb_error)(gb, GB_INVALID_WRITE, addr);
+	PGB_UNREACHABLE();
 }
 
 uint8_t __gb_execute_cb(struct gb_s *gb)
 {
 	uint8_t inst_cycles;
-	uint8_t cbop = __gb_read(gb, gb->cpu_reg.pc++);
+	uint8_t cbop = __gb_read(gb, gb->cpu_reg.pc.reg++);
 	uint8_t r = (cbop & 0x7);
 	uint8_t b = (cbop >> 3) & 0x7;
 	uint8_t d = (cbop >> 3) & 0x1;
@@ -1036,31 +1097,31 @@ uint8_t __gb_execute_cb(struct gb_s *gb)
 	switch(r)
 	{
 	case 0:
-		val = gb->cpu_reg.b;
+		val = gb->cpu_reg.bc.bytes.b;
 		break;
 
 	case 1:
-		val = gb->cpu_reg.c;
+		val = gb->cpu_reg.bc.bytes.c;
 		break;
 
 	case 2:
-		val = gb->cpu_reg.d;
+		val = gb->cpu_reg.de.bytes.d;
 		break;
 
 	case 3:
-		val = gb->cpu_reg.e;
+		val = gb->cpu_reg.de.bytes.e;
 		break;
 
 	case 4:
-		val = gb->cpu_reg.h;
+		val = gb->cpu_reg.hl.bytes.h;
 		break;
 
 	case 5:
-		val = gb->cpu_reg.l;
+		val = gb->cpu_reg.hl.bytes.l;
 		break;
 
 	case 6:
-		val = __gb_read(gb, gb->cpu_reg.hl);
+		val = __gb_read(gb, gb->cpu_reg.hl.reg);
 		break;
 
 	/* Only values 0-7 are possible here, so we make the final case
@@ -1169,31 +1230,31 @@ uint8_t __gb_execute_cb(struct gb_s *gb)
 		switch(r)
 		{
 		case 0:
-			gb->cpu_reg.b = val;
+			gb->cpu_reg.bc.bytes.b = val;
 			break;
 
 		case 1:
-			gb->cpu_reg.c = val;
+			gb->cpu_reg.bc.bytes.c = val;
 			break;
 
 		case 2:
-			gb->cpu_reg.d = val;
+			gb->cpu_reg.de.bytes.d = val;
 			break;
 
 		case 3:
-			gb->cpu_reg.e = val;
+			gb->cpu_reg.de.bytes.e = val;
 			break;
 
 		case 4:
-			gb->cpu_reg.h = val;
+			gb->cpu_reg.hl.bytes.h = val;
 			break;
 
 		case 5:
-			gb->cpu_reg.l = val;
+			gb->cpu_reg.hl.bytes.l = val;
 			break;
 
 		case 6:
-			__gb_write(gb, gb->cpu_reg.hl, val);
+			__gb_write(gb, gb->cpu_reg.hl.reg, val);
 			break;
 
 		case 7:
@@ -1205,6 +1266,26 @@ uint8_t __gb_execute_cb(struct gb_s *gb)
 }
 
 #if ENABLE_LCD
+struct sprite_data {
+	uint8_t sprite_number;
+	uint8_t x;
+};
+
+#if PEANUT_GB_HIGH_LCD_ACCURACY
+static int compare_sprites(const void *in1, const void *in2)
+{
+	const struct sprite_data *sd1, *sd2;
+       
+	sd1 = (struct sprite_data *)in1;
+	sd2 = (struct sprite_data *)in2;
+	int x_res = (int)sd1->x - (int)sd2->x;
+	if(x_res != 0)
+		return x_res;
+
+	return (int)sd1->sprite_number - (int)sd2->sprite_number;
+}
+#endif
+
 void __gb_draw_line(struct gb_s *gb)
 {
 	uint8_t pixels[160] = {0};
@@ -1221,14 +1302,14 @@ void __gb_draw_line(struct gb_s *gb)
 	if(gb->direct.interlace)
 	{
 		if((gb->display.interlace_count == 0
-				&& (gb->gb_reg.LY & 1) == 0)
+				&& (gb->hram_io[IO_LY] & 1) == 0)
 				|| (gb->display.interlace_count == 1
-				    && (gb->gb_reg.LY & 1) == 1))
+				    && (gb->hram_io[IO_LY] & 1) == 1))
 		{
 			/* Compensate for missing window draw if required. */
-			if(gb->gb_reg.LCDC & LCDC_WINDOW_ENABLE
-					&& gb->gb_reg.LY >= gb->display.WY
-					&& gb->gb_reg.WX <= 166)
+			if(gb->hram_io[IO_LCDC] & LCDC_WINDOW_ENABLE
+					&& gb->hram_io[IO_LY] >= gb->display.WY
+					&& gb->hram_io[IO_WX] <= 166)
 				gb->display.window_clear++;
 
 			return;
@@ -1236,19 +1317,19 @@ void __gb_draw_line(struct gb_s *gb)
 	}
 
 	/* If background is enabled, draw it. */
-	if(gb->gb_reg.LCDC & LCDC_BG_ENABLE)
+	if(gb->hram_io[IO_LCDC] & LCDC_BG_ENABLE)
 	{
 		/* Calculate current background line to draw. Constant because
 		 * this function draws only this one line each time it is
 		 * called. */
-		const uint8_t bg_y = gb->gb_reg.LY + gb->gb_reg.SCY;
+		const uint8_t bg_y = gb->hram_io[IO_LY] + gb->hram_io[IO_SCY];
 
 		/* Get selected background map address for first tile
 		 * corresponding to current line.
 		 * 0x20 (32) is the width of a background tile, and the bit
 		 * shift is to calculate the address. */
 		const uint16_t bg_map =
-			((gb->gb_reg.LCDC & LCDC_BG_MAP) ?
+			((gb->hram_io[IO_LCDC] & LCDC_BG_MAP) ?
 			 VRAM_BMAP_2 : VRAM_BMAP_1)
 			+ (bg_y >> 3) * 0x20;
 
@@ -1257,7 +1338,7 @@ void __gb_draw_line(struct gb_s *gb)
 		uint8_t disp_x = LCD_WIDTH - 1;
 
 		/* The X coordinate to begin drawing the background at. */
-		uint8_t bg_x = disp_x + gb->gb_reg.SCX;
+		uint8_t bg_x = disp_x + gb->hram_io[IO_SCX];
 
 		/* Get tile index for current background tile. */
 		uint8_t idx = gb->vram[bg_map + (bg_x >> 3)];
@@ -1269,7 +1350,7 @@ void __gb_draw_line(struct gb_s *gb)
 		uint16_t tile;
 
 		/* Select addressing mode. */
-		if(gb->gb_reg.LCDC & LCDC_TILE_SELECT)
+		if(gb->hram_io[IO_LCDC] & LCDC_TILE_SELECT)
 			tile = VRAM_TILES_1 + idx * 0x10;
 		else
 			tile = VRAM_TILES_2 + ((idx + 0x80) % 0x100) * 0x10;
@@ -1286,10 +1367,10 @@ void __gb_draw_line(struct gb_s *gb)
 			{
 				/* fetch next tile */
 				px = 0;
-				bg_x = disp_x + gb->gb_reg.SCX;
+				bg_x = disp_x + gb->hram_io[IO_SCX];
 				idx = gb->vram[bg_map + (bg_x >> 3)];
 
-				if(gb->gb_reg.LCDC & LCDC_TILE_SELECT)
+				if(gb->hram_io[IO_LCDC] & LCDC_TILE_SELECT)
 					tile = VRAM_TILES_1 + idx * 0x10;
 				else
 					tile = VRAM_TILES_2 + ((idx + 0x80) % 0x100) * 0x10;
@@ -1310,17 +1391,17 @@ void __gb_draw_line(struct gb_s *gb)
 	}
 
 	/* draw window */
-	if(gb->gb_reg.LCDC & LCDC_WINDOW_ENABLE
-			&& gb->gb_reg.LY >= gb->display.WY
-			&& gb->gb_reg.WX <= 166)
+	if(gb->hram_io[IO_LCDC] & LCDC_WINDOW_ENABLE
+			&& gb->hram_io[IO_LY] >= gb->display.WY
+			&& gb->hram_io[IO_WX] <= 166)
 	{
 		/* Calculate Window Map Address. */
-		uint16_t win_line = (gb->gb_reg.LCDC & LCDC_WINDOW_MAP) ?
+		uint16_t win_line = (gb->hram_io[IO_LCDC] & LCDC_WINDOW_MAP) ?
 				    VRAM_BMAP_2 : VRAM_BMAP_1;
 		win_line += (gb->display.window_clear >> 3) * 0x20;
 
 		uint8_t disp_x = LCD_WIDTH - 1;
-		uint8_t win_x = disp_x - gb->gb_reg.WX + 7;
+		uint8_t win_x = disp_x - gb->hram_io[IO_WX] + 7;
 
 		// look up tile
 		uint8_t py = gb->display.window_clear & 0x07;
@@ -1329,7 +1410,7 @@ void __gb_draw_line(struct gb_s *gb)
 
 		uint16_t tile;
 
-		if(gb->gb_reg.LCDC & LCDC_TILE_SELECT)
+		if(gb->hram_io[IO_LCDC] & LCDC_TILE_SELECT)
 			tile = VRAM_TILES_1 + idx * 0x10;
 		else
 			tile = VRAM_TILES_2 + ((idx + 0x80) % 0x100) * 0x10;
@@ -1341,7 +1422,7 @@ void __gb_draw_line(struct gb_s *gb)
 		uint8_t t2 = gb->vram[tile + 1] >> px;
 
 		// loop & copy window
-		uint8_t end = (gb->gb_reg.WX < 7 ? 0 : gb->gb_reg.WX - 7) - 1;
+		uint8_t end = (gb->hram_io[IO_WX] < 7 ? 0 : gb->hram_io[IO_WX] - 7) - 1;
 
 		for(; disp_x != end; disp_x--)
 		{
@@ -1349,10 +1430,10 @@ void __gb_draw_line(struct gb_s *gb)
 			{
 				// fetch next tile
 				px = 0;
-				win_x = disp_x - gb->gb_reg.WX + 7;
+				win_x = disp_x - gb->hram_io[IO_WX] + 7;
 				idx = gb->vram[win_line + (win_x >> 3)];
 
-				if(gb->gb_reg.LCDC & LCDC_TILE_SELECT)
+				if(gb->hram_io[IO_LCDC] & LCDC_TILE_SELECT)
 					tile = VRAM_TILES_1 + idx * 0x10;
 				else
 					tile = VRAM_TILES_2 + ((idx + 0x80) % 0x100) * 0x10;
@@ -1375,42 +1456,86 @@ void __gb_draw_line(struct gb_s *gb)
 	}
 
 	// draw sprites
-	if(gb->gb_reg.LCDC & LCDC_OBJ_ENABLE)
+	if(gb->hram_io[IO_LCDC] & LCDC_OBJ_ENABLE)
 	{
-		uint8_t count = 0;
+#if PEANUT_GB_HIGH_LCD_ACCURACY
+		uint8_t number_of_sprites = 0;
+		struct sprite_data sprites_to_render[NUM_SPRITES];
 
-		for(uint8_t s = NUM_SPRITES - 1;
-				s != 0xFF /* && count < MAX_SPRITES_LINE */ ;
-				s--)
+		/* Record number of sprites on the line being rendered, limited
+		 * to the maximum number sprites that the Game Boy is able to
+		 * render on each line (10 sprites). */
+		for(uint8_t sprite_number = 0;
+				sprite_number < PEANUT_GB_ARRAYSIZE(sprites_to_render);
+				sprite_number++)
 		{
+			/* Sprite Y position. */
+			uint8_t OY = gb->oam[4 * sprite_number + 0];
+			/* Sprite X position. */
+			uint8_t OX = gb->oam[4 * sprite_number + 1];
+
+			/* If sprite isn't on this line, continue. */
+			if (gb->hram_io[IO_LY] +
+				(gb->hram_io[IO_LCDC] & LCDC_OBJ_SIZE ? 0 : 8) >= OY
+					|| gb->hram_io[IO_LY] + 16 < OY)
+				continue;
+
+
+			sprites_to_render[number_of_sprites].sprite_number = sprite_number;
+			sprites_to_render[number_of_sprites].x = OX;
+			number_of_sprites++;
+		}
+
+		/* If maximum number of sprites reached, prioritise X
+		 * coordinate and object location in OAM. */
+		qsort(&sprites_to_render[0], number_of_sprites,
+				sizeof(sprites_to_render[0]), compare_sprites);
+		if(number_of_sprites > MAX_SPRITES_LINE)
+			number_of_sprites = MAX_SPRITES_LINE;
+#endif
+
+		/* Render each sprite, from low priority to high priority. */
+#if PEANUT_GB_HIGH_LCD_ACCURACY
+		/* Render the top ten prioritised sprites on this scanline. */
+		for(uint8_t sprite_number = number_of_sprites - 1;
+				sprite_number != 0xFF;
+				sprite_number--)
+		{
+			uint8_t s = sprites_to_render[sprite_number].sprite_number;
+#else
+		for (uint8_t sprite_number = NUM_SPRITES - 1;
+			sprite_number != 0xFF;
+			sprite_number--)
+		{
+			uint8_t s = sprite_number;
+#endif
 			/* Sprite Y position. */
 			uint8_t OY = gb->oam[4 * s + 0];
 			/* Sprite X position. */
 			uint8_t OX = gb->oam[4 * s + 1];
 			/* Sprite Tile/Pattern Number. */
 			uint8_t OT = gb->oam[4 * s + 2]
-				     & (gb->gb_reg.LCDC & LCDC_OBJ_SIZE ? 0xFE : 0xFF);
+				     & (gb->hram_io[IO_LCDC] & LCDC_OBJ_SIZE ? 0xFE : 0xFF);
 			/* Additional attributes. */
 			uint8_t OF = gb->oam[4 * s + 3];
 
+#if !PEANUT_GB_HIGH_LCD_ACCURACY
 			/* If sprite isn't on this line, continue. */
-			if(gb->gb_reg.LY +
-					(gb->gb_reg.LCDC & LCDC_OBJ_SIZE ?
-					 0 : 8) >= OY
-					|| gb->gb_reg.LY + 16 < OY)
+			if(gb->hram_io[IO_LY] +
+					(gb->hram_io[IO_LCDC] & LCDC_OBJ_SIZE ? 0 : 8) >= OY ||
+					gb->hram_io[IO_LY] + 16 < OY)
 				continue;
-
-			count++;
+#endif
 
 			/* Continue if sprite not visible. */
 			if(OX == 0 || OX >= 168)
 				continue;
 
 			// y flip
-			uint8_t py = gb->gb_reg.LY - OY + 16;
+			uint8_t py = gb->hram_io[IO_LY] - OY + 16;
 
 			if(OF & OBJ_FLIP_Y)
-				py = (gb->gb_reg.LCDC & LCDC_OBJ_SIZE ? 15 : 7) - py;
+				py = (gb->hram_io[IO_LCDC] & LCDC_OBJ_SIZE ? 15 : 7) - py;
 
 			// fetch the tile
 			uint8_t t1 = gb->vram[VRAM_TILES_1 + OT * 0x10 + 2 * py];
@@ -1470,7 +1595,7 @@ void __gb_draw_line(struct gb_s *gb)
 		}
 	}
 
-	gb->display.lcd_draw_line(gb, pixels, gb->gb_reg.LY);
+	gb->display.lcd_draw_line(gb, pixels, gb->hram_io[IO_LY]);
 }
 #endif
 
@@ -1479,7 +1604,8 @@ void __gb_draw_line(struct gb_s *gb)
  */
 void __gb_step_cpu(struct gb_s *gb)
 {
-	uint8_t opcode, inst_cycles;
+	uint8_t opcode;
+	uint_fast16_t inst_cycles;
 	static const uint8_t op_cycles[0x100] =
 	{
 		/* *INDENT-OFF* */
@@ -1491,7 +1617,7 @@ void __gb_step_cpu(struct gb_s *gb)
 		4, 4, 4, 4, 4, 4, 8, 4, 4, 4, 4, 4, 4, 4, 8, 4,	/* 0x40 */
 		4, 4, 4, 4, 4, 4, 8, 4, 4, 4, 4, 4, 4, 4, 8, 4,	/* 0x50 */
 		4, 4, 4, 4, 4, 4, 8, 4, 4, 4, 4, 4, 4, 4, 8, 4,	/* 0x60 */
-		8, 8, 8, 8, 8, 8, 4, 8, 4, 4, 4, 4, 4, 4, 8, 4,	/* 0x70 */
+		8, 8, 8, 8, 8, 8, 4, 8, 4, 4, 4, 4, 4, 4, 8, 4, /* 0x70 */
 		4, 4, 4, 4, 4, 4, 8, 4, 4, 4, 4, 4, 4, 4, 8, 4,	/* 0x80 */
 		4, 4, 4, 4, 4, 4, 8, 4, 4, 4, 4, 4, 4, 4, 8, 4,	/* 0x90 */
 		4, 4, 4, 4, 4, 4, 8, 4, 4, 4, 4, 4, 4, 4, 8, 4,	/* 0xA0 */
@@ -1502,10 +1628,14 @@ void __gb_step_cpu(struct gb_s *gb)
 		12,12,8, 4, 0,16, 8,16,12, 8,16, 4, 0, 0, 8,16	/* 0xF0 */
 		/* *INDENT-ON* */
 	};
+	static const uint_fast16_t TAC_CYCLES[4] = {1024, 16, 64, 256};
 
 	/* Handle interrupts */
-	if((gb->gb_ime || gb->gb_halt) &&
-			(gb->gb_reg.IF & gb->gb_reg.IE & ANY_INTR))
+	/* If gb_halt is positive, then an interrupt must have occured by the
+	 * time we reach here, becuase on HALT, we jump to the next interrupt
+	 * immediately. */
+	if(gb->gb_halt || (gb->gb_ime &&
+			gb->hram_io[IO_IF] & gb->hram_io[IO_IE] & ANY_INTR))
 	{
 		gb->gb_halt = 0;
 
@@ -1515,40 +1645,40 @@ void __gb_step_cpu(struct gb_s *gb)
 			gb->gb_ime = 0;
 
 			/* Push Program Counter */
-			__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc >> 8);
-			__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc & 0xFF);
+			__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.p);
+			__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.c);
 
 			/* Call interrupt handler if required. */
-			if(gb->gb_reg.IF & gb->gb_reg.IE & VBLANK_INTR)
+			if(gb->hram_io[IO_IF] & gb->hram_io[IO_IE] & VBLANK_INTR)
 			{
-				gb->cpu_reg.pc = VBLANK_INTR_ADDR;
-				gb->gb_reg.IF ^= VBLANK_INTR;
+				gb->cpu_reg.pc.reg = VBLANK_INTR_ADDR;
+				gb->hram_io[IO_IF] ^= VBLANK_INTR;
 			}
-			else if(gb->gb_reg.IF & gb->gb_reg.IE & LCDC_INTR)
+			else if(gb->hram_io[IO_IF] & gb->hram_io[IO_IE] & LCDC_INTR)
 			{
-				gb->cpu_reg.pc = LCDC_INTR_ADDR;
-				gb->gb_reg.IF ^= LCDC_INTR;
+				gb->cpu_reg.pc.reg = LCDC_INTR_ADDR;
+				gb->hram_io[IO_IF] ^= LCDC_INTR;
 			}
-			else if(gb->gb_reg.IF & gb->gb_reg.IE & TIMER_INTR)
+			else if(gb->hram_io[IO_IF] & gb->hram_io[IO_IE] & TIMER_INTR)
 			{
-				gb->cpu_reg.pc = TIMER_INTR_ADDR;
-				gb->gb_reg.IF ^= TIMER_INTR;
+				gb->cpu_reg.pc.reg = TIMER_INTR_ADDR;
+				gb->hram_io[IO_IF] ^= TIMER_INTR;
 			}
-			else if(gb->gb_reg.IF & gb->gb_reg.IE & SERIAL_INTR)
+			else if(gb->hram_io[IO_IF] & gb->hram_io[IO_IE] & SERIAL_INTR)
 			{
-				gb->cpu_reg.pc = SERIAL_INTR_ADDR;
-				gb->gb_reg.IF ^= SERIAL_INTR;
+				gb->cpu_reg.pc.reg = SERIAL_INTR_ADDR;
+				gb->hram_io[IO_IF] ^= SERIAL_INTR;
 			}
-			else if(gb->gb_reg.IF & gb->gb_reg.IE & CONTROL_INTR)
+			else if(gb->hram_io[IO_IF] & gb->hram_io[IO_IE] & CONTROL_INTR)
 			{
-				gb->cpu_reg.pc = CONTROL_INTR_ADDR;
-				gb->gb_reg.IF ^= CONTROL_INTR;
+				gb->cpu_reg.pc.reg = CONTROL_INTR_ADDR;
+				gb->hram_io[IO_IF] ^= CONTROL_INTR;
 			}
 		}
 	}
 
 	/* Obtain opcode */
-	opcode = (gb->gb_halt ? 0x00 : __gb_read(gb, gb->cpu_reg.pc++));
+	opcode = __gb_read(gb, gb->cpu_reg.pc.reg++);
 	inst_cycles = op_cycles[opcode];
 
 	/* Execute opcode */
@@ -1558,34 +1688,31 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0x01: /* LD BC, imm */
-		gb->cpu_reg.c = __gb_read(gb, gb->cpu_reg.pc++);
-		gb->cpu_reg.b = __gb_read(gb, gb->cpu_reg.pc++);
+		gb->cpu_reg.bc.bytes.c = __gb_read(gb, gb->cpu_reg.pc.reg++);
+		gb->cpu_reg.bc.bytes.b = __gb_read(gb, gb->cpu_reg.pc.reg++);
 		break;
 
 	case 0x02: /* LD (BC), A */
-		__gb_write(gb, gb->cpu_reg.bc, gb->cpu_reg.a);
+		__gb_write(gb, gb->cpu_reg.bc.reg, gb->cpu_reg.a);
 		break;
 
 	case 0x03: /* INC BC */
-		gb->cpu_reg.bc++;
+		gb->cpu_reg.bc.reg++;
 		break;
 
 	case 0x04: /* INC B */
-		gb->cpu_reg.b++;
-		gb->cpu_reg.f_bits.z = (gb->cpu_reg.b == 0x00);
+		gb->cpu_reg.bc.bytes.b++;
+		gb->cpu_reg.f_bits.z = (gb->cpu_reg.bc.bytes.b == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
-		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.b & 0x0F) == 0x00);
+		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.bc.bytes.b & 0x0F) == 0x00);
 		break;
 
 	case 0x05: /* DEC B */
-		gb->cpu_reg.b--;
-		gb->cpu_reg.f_bits.z = (gb->cpu_reg.b == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.b & 0x0F) == 0x0F);
+		PGB_INSTR_DEC_R8(gb->cpu_reg.bc.bytes.b);
 		break;
 
 	case 0x06: /* LD B, imm */
-		gb->cpu_reg.b = __gb_read(gb, gb->cpu_reg.pc++);
+		gb->cpu_reg.bc.bytes.b = __gb_read(gb, gb->cpu_reg.pc.reg++);
 		break;
 
 	case 0x07: /* RLCA */
@@ -1598,48 +1725,48 @@ void __gb_step_cpu(struct gb_s *gb)
 
 	case 0x08: /* LD (imm), SP */
 	{
-		uint16_t temp = __gb_read(gb, gb->cpu_reg.pc++);
-		temp |= __gb_read(gb, gb->cpu_reg.pc++) << 8;
-		__gb_write(gb, temp++, gb->cpu_reg.sp & 0xFF);
-		__gb_write(gb, temp, gb->cpu_reg.sp >> 8);
+		uint8_t h, l;
+		uint16_t temp;
+		l = __gb_read(gb, gb->cpu_reg.pc.reg++);
+		h = __gb_read(gb, gb->cpu_reg.pc.reg++);
+		temp = PEANUT_GB_U8_TO_U16(h,l);
+		__gb_write(gb, temp++, gb->cpu_reg.sp.bytes.p);
+		__gb_write(gb, temp, gb->cpu_reg.sp.bytes.s);
 		break;
 	}
 
 	case 0x09: /* ADD HL, BC */
 	{
-		uint_fast32_t temp = gb->cpu_reg.hl + gb->cpu_reg.bc;
+		uint_fast32_t temp = gb->cpu_reg.hl.reg + gb->cpu_reg.bc.reg;
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h =
-			(temp ^ gb->cpu_reg.hl ^ gb->cpu_reg.bc) & 0x1000 ? 1 : 0;
+			(temp ^ gb->cpu_reg.hl.reg ^ gb->cpu_reg.bc.reg) & 0x1000 ? 1 : 0;
 		gb->cpu_reg.f_bits.c = (temp & 0xFFFF0000) ? 1 : 0;
-		gb->cpu_reg.hl = (temp & 0x0000FFFF);
+		gb->cpu_reg.hl.reg = (temp & 0x0000FFFF);
 		break;
 	}
 
 	case 0x0A: /* LD A, (BC) */
-		gb->cpu_reg.a = __gb_read(gb, gb->cpu_reg.bc);
+		gb->cpu_reg.a = __gb_read(gb, gb->cpu_reg.bc.reg);
 		break;
 
 	case 0x0B: /* DEC BC */
-		gb->cpu_reg.bc--;
+		gb->cpu_reg.bc.reg--;
 		break;
 
 	case 0x0C: /* INC C */
-		gb->cpu_reg.c++;
-		gb->cpu_reg.f_bits.z = (gb->cpu_reg.c == 0x00);
+		gb->cpu_reg.bc.bytes.c++;
+		gb->cpu_reg.f_bits.z = (gb->cpu_reg.bc.bytes.c == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
-		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.c & 0x0F) == 0x00);
+		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.bc.bytes.c & 0x0F) == 0x00);
 		break;
 
 	case 0x0D: /* DEC C */
-		gb->cpu_reg.c--;
-		gb->cpu_reg.f_bits.z = (gb->cpu_reg.c == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.c & 0x0F) == 0x0F);
+		PGB_INSTR_DEC_R8(gb->cpu_reg.bc.bytes.c);
 		break;
 
 	case 0x0E: /* LD C, imm */
-		gb->cpu_reg.c = __gb_read(gb, gb->cpu_reg.pc++);
+		gb->cpu_reg.bc.bytes.c = __gb_read(gb, gb->cpu_reg.pc.reg++);
 		break;
 
 	case 0x0F: /* RRCA */
@@ -1655,34 +1782,31 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0x11: /* LD DE, imm */
-		gb->cpu_reg.e = __gb_read(gb, gb->cpu_reg.pc++);
-		gb->cpu_reg.d = __gb_read(gb, gb->cpu_reg.pc++);
+		gb->cpu_reg.de.bytes.e = __gb_read(gb, gb->cpu_reg.pc.reg++);
+		gb->cpu_reg.de.bytes.d = __gb_read(gb, gb->cpu_reg.pc.reg++);
 		break;
 
 	case 0x12: /* LD (DE), A */
-		__gb_write(gb, gb->cpu_reg.de, gb->cpu_reg.a);
+		__gb_write(gb, gb->cpu_reg.de.reg, gb->cpu_reg.a);
 		break;
 
 	case 0x13: /* INC DE */
-		gb->cpu_reg.de++;
+		gb->cpu_reg.de.reg++;
 		break;
 
 	case 0x14: /* INC D */
-		gb->cpu_reg.d++;
-		gb->cpu_reg.f_bits.z = (gb->cpu_reg.d == 0x00);
+		gb->cpu_reg.de.bytes.d++;
+		gb->cpu_reg.f_bits.z = (gb->cpu_reg.de.bytes.d == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
-		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.d & 0x0F) == 0x00);
+		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.de.bytes.d & 0x0F) == 0x00);
 		break;
 
 	case 0x15: /* DEC D */
-		gb->cpu_reg.d--;
-		gb->cpu_reg.f_bits.z = (gb->cpu_reg.d == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.d & 0x0F) == 0x0F);
+		PGB_INSTR_DEC_R8(gb->cpu_reg.de.bytes.d);
 		break;
 
 	case 0x16: /* LD D, imm */
-		gb->cpu_reg.d = __gb_read(gb, gb->cpu_reg.pc++);
+		gb->cpu_reg.de.bytes.d = __gb_read(gb, gb->cpu_reg.pc.reg++);
 		break;
 
 	case 0x17: /* RLA */
@@ -1698,46 +1822,43 @@ void __gb_step_cpu(struct gb_s *gb)
 
 	case 0x18: /* JR imm */
 	{
-		int8_t temp = (int8_t) __gb_read(gb, gb->cpu_reg.pc++);
-		gb->cpu_reg.pc += temp;
+		int8_t temp = (int8_t) __gb_read(gb, gb->cpu_reg.pc.reg++);
+		gb->cpu_reg.pc.reg += temp;
 		break;
 	}
 
 	case 0x19: /* ADD HL, DE */
 	{
-		uint_fast32_t temp = gb->cpu_reg.hl + gb->cpu_reg.de;
+		uint_fast32_t temp = gb->cpu_reg.hl.reg + gb->cpu_reg.de.reg;
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h =
-			(temp ^ gb->cpu_reg.hl ^ gb->cpu_reg.de) & 0x1000 ? 1 : 0;
+			(temp ^ gb->cpu_reg.hl.reg ^ gb->cpu_reg.de.reg) & 0x1000 ? 1 : 0;
 		gb->cpu_reg.f_bits.c = (temp & 0xFFFF0000) ? 1 : 0;
-		gb->cpu_reg.hl = (temp & 0x0000FFFF);
+		gb->cpu_reg.hl.reg = (temp & 0x0000FFFF);
 		break;
 	}
 
 	case 0x1A: /* LD A, (DE) */
-		gb->cpu_reg.a = __gb_read(gb, gb->cpu_reg.de);
+		gb->cpu_reg.a = __gb_read(gb, gb->cpu_reg.de.reg);
 		break;
 
 	case 0x1B: /* DEC DE */
-		gb->cpu_reg.de--;
+		gb->cpu_reg.de.reg--;
 		break;
 
 	case 0x1C: /* INC E */
-		gb->cpu_reg.e++;
-		gb->cpu_reg.f_bits.z = (gb->cpu_reg.e == 0x00);
+		gb->cpu_reg.de.bytes.e++;
+		gb->cpu_reg.f_bits.z = (gb->cpu_reg.de.bytes.e == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
-		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.e & 0x0F) == 0x00);
+		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.de.bytes.e & 0x0F) == 0x00);
 		break;
 
 	case 0x1D: /* DEC E */
-		gb->cpu_reg.e--;
-		gb->cpu_reg.f_bits.z = (gb->cpu_reg.e == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.e & 0x0F) == 0x0F);
+		PGB_INSTR_DEC_R8(gb->cpu_reg.de.bytes.e);
 		break;
 
 	case 0x1E: /* LD E, imm */
-		gb->cpu_reg.e = __gb_read(gb, gb->cpu_reg.pc++);
+		gb->cpu_reg.de.bytes.e = __gb_read(gb, gb->cpu_reg.pc.reg++);
 		break;
 
 	case 0x1F: /* RRA */
@@ -1751,53 +1872,51 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 	}
 
-	case 0x20: /* JP NZ, imm */
+	case 0x20: /* JR NZ, imm */
 		if(!gb->cpu_reg.f_bits.z)
 		{
-			int8_t temp = (int8_t) __gb_read(gb, gb->cpu_reg.pc++);
-			gb->cpu_reg.pc += temp;
+			int8_t temp = (int8_t) __gb_read(gb, gb->cpu_reg.pc.reg++);
+			gb->cpu_reg.pc.reg += temp;
 			inst_cycles += 4;
 		}
 		else
-			gb->cpu_reg.pc++;
+			gb->cpu_reg.pc.reg++;
 
 		break;
 
 	case 0x21: /* LD HL, imm */
-		gb->cpu_reg.l = __gb_read(gb, gb->cpu_reg.pc++);
-		gb->cpu_reg.h = __gb_read(gb, gb->cpu_reg.pc++);
+		gb->cpu_reg.hl.bytes.l = __gb_read(gb, gb->cpu_reg.pc.reg++);
+		gb->cpu_reg.hl.bytes.h = __gb_read(gb, gb->cpu_reg.pc.reg++);
 		break;
 
 	case 0x22: /* LDI (HL), A */
-		__gb_write(gb, gb->cpu_reg.hl, gb->cpu_reg.a);
-		gb->cpu_reg.hl++;
+		__gb_write(gb, gb->cpu_reg.hl.reg, gb->cpu_reg.a);
+		gb->cpu_reg.hl.reg++;
 		break;
 
 	case 0x23: /* INC HL */
-		gb->cpu_reg.hl++;
+		gb->cpu_reg.hl.reg++;
 		break;
 
 	case 0x24: /* INC H */
-		gb->cpu_reg.h++;
-		gb->cpu_reg.f_bits.z = (gb->cpu_reg.h == 0x00);
+		gb->cpu_reg.hl.bytes.h++;
+		gb->cpu_reg.f_bits.z = (gb->cpu_reg.hl.bytes.h == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
-		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.h & 0x0F) == 0x00);
+		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.hl.bytes.h & 0x0F) == 0x00);
 		break;
 
 	case 0x25: /* DEC H */
-		gb->cpu_reg.h--;
-		gb->cpu_reg.f_bits.z = (gb->cpu_reg.h == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.h & 0x0F) == 0x0F);
+		PGB_INSTR_DEC_R8(gb->cpu_reg.hl.bytes.h);
 		break;
 
 	case 0x26: /* LD H, imm */
-		gb->cpu_reg.h = __gb_read(gb, gb->cpu_reg.pc++);
+		gb->cpu_reg.hl.bytes.h = __gb_read(gb, gb->cpu_reg.pc.reg++);
 		break;
 
 	case 0x27: /* DAA */
 	{
-		uint16_t a = gb->cpu_reg.a;
+		/* The following is from SameBoy. MIT License. */
+		int16_t a = gb->cpu_reg.a;
 
 		if(gb->cpu_reg.f_bits.n)
 		{
@@ -1829,49 +1948,45 @@ void __gb_step_cpu(struct gb_s *gb)
 	case 0x28: /* JP Z, imm */
 		if(gb->cpu_reg.f_bits.z)
 		{
-			int8_t temp = (int8_t) __gb_read(gb, gb->cpu_reg.pc++);
-			gb->cpu_reg.pc += temp;
+			int8_t temp = (int8_t) __gb_read(gb, gb->cpu_reg.pc.reg++);
+			gb->cpu_reg.pc.reg += temp;
 			inst_cycles += 4;
 		}
 		else
-			gb->cpu_reg.pc++;
+			gb->cpu_reg.pc.reg++;
 
 		break;
 
 	case 0x29: /* ADD HL, HL */
 	{
-		uint_fast32_t temp = gb->cpu_reg.hl + gb->cpu_reg.hl;
+		gb->cpu_reg.f_bits.c = (gb->cpu_reg.hl.reg & 0x8000) > 0;
+		gb->cpu_reg.hl.reg <<= 1;
 		gb->cpu_reg.f_bits.n = 0;
-		gb->cpu_reg.f_bits.h = (temp & 0x1000) ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFFFF0000) ? 1 : 0;
-		gb->cpu_reg.hl = (temp & 0x0000FFFF);
+		gb->cpu_reg.f_bits.h = (gb->cpu_reg.hl.reg & 0x1000) > 0;
 		break;
 	}
 
 	case 0x2A: /* LD A, (HL+) */
-		gb->cpu_reg.a = __gb_read(gb, gb->cpu_reg.hl++);
+		gb->cpu_reg.a = __gb_read(gb, gb->cpu_reg.hl.reg++);
 		break;
 
 	case 0x2B: /* DEC HL */
-		gb->cpu_reg.hl--;
+		gb->cpu_reg.hl.reg--;
 		break;
 
 	case 0x2C: /* INC L */
-		gb->cpu_reg.l++;
-		gb->cpu_reg.f_bits.z = (gb->cpu_reg.l == 0x00);
+		gb->cpu_reg.hl.bytes.l++;
+		gb->cpu_reg.f_bits.z = (gb->cpu_reg.hl.bytes.l == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
-		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.l & 0x0F) == 0x00);
+		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.hl.bytes.l & 0x0F) == 0x00);
 		break;
 
 	case 0x2D: /* DEC L */
-		gb->cpu_reg.l--;
-		gb->cpu_reg.f_bits.z = (gb->cpu_reg.l == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.l & 0x0F) == 0x0F);
+		PGB_INSTR_DEC_R8(gb->cpu_reg.hl.bytes.l);
 		break;
 
 	case 0x2E: /* LD L, imm */
-		gb->cpu_reg.l = __gb_read(gb, gb->cpu_reg.pc++);
+		gb->cpu_reg.hl.bytes.l = __gb_read(gb, gb->cpu_reg.pc.reg++);
 		break;
 
 	case 0x2F: /* CPL */
@@ -1883,51 +1998,51 @@ void __gb_step_cpu(struct gb_s *gb)
 	case 0x30: /* JP NC, imm */
 		if(!gb->cpu_reg.f_bits.c)
 		{
-			int8_t temp = (int8_t) __gb_read(gb, gb->cpu_reg.pc++);
-			gb->cpu_reg.pc += temp;
+			int8_t temp = (int8_t) __gb_read(gb, gb->cpu_reg.pc.reg++);
+			gb->cpu_reg.pc.reg += temp;
 			inst_cycles += 4;
 		}
 		else
-			gb->cpu_reg.pc++;
+			gb->cpu_reg.pc.reg++;
 
 		break;
 
 	case 0x31: /* LD SP, imm */
-		gb->cpu_reg.sp = __gb_read(gb, gb->cpu_reg.pc++);
-		gb->cpu_reg.sp |= __gb_read(gb, gb->cpu_reg.pc++) << 8;
+		gb->cpu_reg.sp.bytes.p = __gb_read(gb, gb->cpu_reg.pc.reg++);
+		gb->cpu_reg.sp.bytes.s = __gb_read(gb, gb->cpu_reg.pc.reg++);
 		break;
 
 	case 0x32: /* LD (HL), A */
-		__gb_write(gb, gb->cpu_reg.hl, gb->cpu_reg.a);
-		gb->cpu_reg.hl--;
+		__gb_write(gb, gb->cpu_reg.hl.reg, gb->cpu_reg.a);
+		gb->cpu_reg.hl.reg--;
 		break;
 
 	case 0x33: /* INC SP */
-		gb->cpu_reg.sp++;
+		gb->cpu_reg.sp.reg++;
 		break;
 
 	case 0x34: /* INC (HL) */
 	{
-		uint8_t temp = __gb_read(gb, gb->cpu_reg.hl) + 1;
+		uint8_t temp = __gb_read(gb, gb->cpu_reg.hl.reg) + 1;
 		gb->cpu_reg.f_bits.z = (temp == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h = ((temp & 0x0F) == 0x00);
-		__gb_write(gb, gb->cpu_reg.hl, temp);
+		__gb_write(gb, gb->cpu_reg.hl.reg, temp);
 		break;
 	}
 
 	case 0x35: /* DEC (HL) */
 	{
-		uint8_t temp = __gb_read(gb, gb->cpu_reg.hl) - 1;
+		uint8_t temp = __gb_read(gb, gb->cpu_reg.hl.reg) - 1;
 		gb->cpu_reg.f_bits.z = (temp == 0x00);
 		gb->cpu_reg.f_bits.n = 1;
 		gb->cpu_reg.f_bits.h = ((temp & 0x0F) == 0x0F);
-		__gb_write(gb, gb->cpu_reg.hl, temp);
+		__gb_write(gb, gb->cpu_reg.hl.reg, temp);
 		break;
 	}
 
 	case 0x36: /* LD (HL), imm */
-		__gb_write(gb, gb->cpu_reg.hl, __gb_read(gb, gb->cpu_reg.pc++));
+		__gb_write(gb, gb->cpu_reg.hl.reg, __gb_read(gb, gb->cpu_reg.pc.reg++));
 		break;
 
 	case 0x37: /* SCF */
@@ -1939,32 +2054,32 @@ void __gb_step_cpu(struct gb_s *gb)
 	case 0x38: /* JP C, imm */
 		if(gb->cpu_reg.f_bits.c)
 		{
-			int8_t temp = (int8_t) __gb_read(gb, gb->cpu_reg.pc++);
-			gb->cpu_reg.pc += temp;
+			int8_t temp = (int8_t) __gb_read(gb, gb->cpu_reg.pc.reg++);
+			gb->cpu_reg.pc.reg += temp;
 			inst_cycles += 4;
 		}
 		else
-			gb->cpu_reg.pc++;
+			gb->cpu_reg.pc.reg++;
 
 		break;
 
 	case 0x39: /* ADD HL, SP */
 	{
-		uint_fast32_t temp = gb->cpu_reg.hl + gb->cpu_reg.sp;
+		uint_fast32_t temp = gb->cpu_reg.hl.reg + gb->cpu_reg.sp.reg;
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h =
-			((gb->cpu_reg.hl & 0xFFF) + (gb->cpu_reg.sp & 0xFFF)) & 0x1000 ? 1 : 0;
+			((gb->cpu_reg.hl.reg & 0xFFF) + (gb->cpu_reg.sp.reg & 0xFFF)) & 0x1000 ? 1 : 0;
 		gb->cpu_reg.f_bits.c = temp & 0x10000 ? 1 : 0;
-		gb->cpu_reg.hl = (uint16_t)temp;
+		gb->cpu_reg.hl.reg = (uint16_t)temp;
 		break;
 	}
 
 	case 0x3A: /* LD A, (HL) */
-		gb->cpu_reg.a = __gb_read(gb, gb->cpu_reg.hl--);
+		gb->cpu_reg.a = __gb_read(gb, gb->cpu_reg.hl.reg--);
 		break;
 
 	case 0x3B: /* DEC SP */
-		gb->cpu_reg.sp--;
+		gb->cpu_reg.sp.reg--;
 		break;
 
 	case 0x3C: /* INC A */
@@ -1982,7 +2097,7 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0x3E: /* LD A, imm */
-		gb->cpu_reg.a = __gb_read(gb, gb->cpu_reg.pc++);
+		gb->cpu_reg.a = __gb_read(gb, gb->cpu_reg.pc.reg++);
 		break;
 
 	case 0x3F: /* CCF */
@@ -1995,533 +2110,412 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0x41: /* LD B, C */
-		gb->cpu_reg.b = gb->cpu_reg.c;
+		gb->cpu_reg.bc.bytes.b = gb->cpu_reg.bc.bytes.c;
 		break;
 
 	case 0x42: /* LD B, D */
-		gb->cpu_reg.b = gb->cpu_reg.d;
+		gb->cpu_reg.bc.bytes.b = gb->cpu_reg.de.bytes.d;
 		break;
 
 	case 0x43: /* LD B, E */
-		gb->cpu_reg.b = gb->cpu_reg.e;
+		gb->cpu_reg.bc.bytes.b = gb->cpu_reg.de.bytes.e;
 		break;
 
 	case 0x44: /* LD B, H */
-		gb->cpu_reg.b = gb->cpu_reg.h;
+		gb->cpu_reg.bc.bytes.b = gb->cpu_reg.hl.bytes.h;
 		break;
 
 	case 0x45: /* LD B, L */
-		gb->cpu_reg.b = gb->cpu_reg.l;
+		gb->cpu_reg.bc.bytes.b = gb->cpu_reg.hl.bytes.l;
 		break;
 
 	case 0x46: /* LD B, (HL) */
-		gb->cpu_reg.b = __gb_read(gb, gb->cpu_reg.hl);
+		gb->cpu_reg.bc.bytes.b = __gb_read(gb, gb->cpu_reg.hl.reg);
 		break;
 
 	case 0x47: /* LD B, A */
-		gb->cpu_reg.b = gb->cpu_reg.a;
+		gb->cpu_reg.bc.bytes.b = gb->cpu_reg.a;
 		break;
 
 	case 0x48: /* LD C, B */
-		gb->cpu_reg.c = gb->cpu_reg.b;
+		gb->cpu_reg.bc.bytes.c = gb->cpu_reg.bc.bytes.b;
 		break;
 
 	case 0x49: /* LD C, C */
 		break;
 
 	case 0x4A: /* LD C, D */
-		gb->cpu_reg.c = gb->cpu_reg.d;
+		gb->cpu_reg.bc.bytes.c = gb->cpu_reg.de.bytes.d;
 		break;
 
 	case 0x4B: /* LD C, E */
-		gb->cpu_reg.c = gb->cpu_reg.e;
+		gb->cpu_reg.bc.bytes.c = gb->cpu_reg.de.bytes.e;
 		break;
 
 	case 0x4C: /* LD C, H */
-		gb->cpu_reg.c = gb->cpu_reg.h;
+		gb->cpu_reg.bc.bytes.c = gb->cpu_reg.hl.bytes.h;
 		break;
 
 	case 0x4D: /* LD C, L */
-		gb->cpu_reg.c = gb->cpu_reg.l;
+		gb->cpu_reg.bc.bytes.c = gb->cpu_reg.hl.bytes.l;
 		break;
 
 	case 0x4E: /* LD C, (HL) */
-		gb->cpu_reg.c = __gb_read(gb, gb->cpu_reg.hl);
+		gb->cpu_reg.bc.bytes.c = __gb_read(gb, gb->cpu_reg.hl.reg);
 		break;
 
 	case 0x4F: /* LD C, A */
-		gb->cpu_reg.c = gb->cpu_reg.a;
+		gb->cpu_reg.bc.bytes.c = gb->cpu_reg.a;
 		break;
 
 	case 0x50: /* LD D, B */
-		gb->cpu_reg.d = gb->cpu_reg.b;
+		gb->cpu_reg.de.bytes.d = gb->cpu_reg.bc.bytes.b;
 		break;
 
 	case 0x51: /* LD D, C */
-		gb->cpu_reg.d = gb->cpu_reg.c;
+		gb->cpu_reg.de.bytes.d = gb->cpu_reg.bc.bytes.c;
 		break;
 
 	case 0x52: /* LD D, D */
 		break;
 
 	case 0x53: /* LD D, E */
-		gb->cpu_reg.d = gb->cpu_reg.e;
+		gb->cpu_reg.de.bytes.d = gb->cpu_reg.de.bytes.e;
 		break;
 
 	case 0x54: /* LD D, H */
-		gb->cpu_reg.d = gb->cpu_reg.h;
+		gb->cpu_reg.de.bytes.d = gb->cpu_reg.hl.bytes.h;
 		break;
 
 	case 0x55: /* LD D, L */
-		gb->cpu_reg.d = gb->cpu_reg.l;
+		gb->cpu_reg.de.bytes.d = gb->cpu_reg.hl.bytes.l;
 		break;
 
 	case 0x56: /* LD D, (HL) */
-		gb->cpu_reg.d = __gb_read(gb, gb->cpu_reg.hl);
+		gb->cpu_reg.de.bytes.d = __gb_read(gb, gb->cpu_reg.hl.reg);
 		break;
 
 	case 0x57: /* LD D, A */
-		gb->cpu_reg.d = gb->cpu_reg.a;
+		gb->cpu_reg.de.bytes.d = gb->cpu_reg.a;
 		break;
 
 	case 0x58: /* LD E, B */
-		gb->cpu_reg.e = gb->cpu_reg.b;
+		gb->cpu_reg.de.bytes.e = gb->cpu_reg.bc.bytes.b;
 		break;
 
 	case 0x59: /* LD E, C */
-		gb->cpu_reg.e = gb->cpu_reg.c;
+		gb->cpu_reg.de.bytes.e = gb->cpu_reg.bc.bytes.c;
 		break;
 
 	case 0x5A: /* LD E, D */
-		gb->cpu_reg.e = gb->cpu_reg.d;
+		gb->cpu_reg.de.bytes.e = gb->cpu_reg.de.bytes.d;
 		break;
 
 	case 0x5B: /* LD E, E */
 		break;
 
 	case 0x5C: /* LD E, H */
-		gb->cpu_reg.e = gb->cpu_reg.h;
+		gb->cpu_reg.de.bytes.e = gb->cpu_reg.hl.bytes.h;
 		break;
 
 	case 0x5D: /* LD E, L */
-		gb->cpu_reg.e = gb->cpu_reg.l;
+		gb->cpu_reg.de.bytes.e = gb->cpu_reg.hl.bytes.l;
 		break;
 
 	case 0x5E: /* LD E, (HL) */
-		gb->cpu_reg.e = __gb_read(gb, gb->cpu_reg.hl);
+		gb->cpu_reg.de.bytes.e = __gb_read(gb, gb->cpu_reg.hl.reg);
 		break;
 
 	case 0x5F: /* LD E, A */
-		gb->cpu_reg.e = gb->cpu_reg.a;
+		gb->cpu_reg.de.bytes.e = gb->cpu_reg.a;
 		break;
 
 	case 0x60: /* LD H, B */
-		gb->cpu_reg.h = gb->cpu_reg.b;
+		gb->cpu_reg.hl.bytes.h = gb->cpu_reg.bc.bytes.b;
 		break;
 
 	case 0x61: /* LD H, C */
-		gb->cpu_reg.h = gb->cpu_reg.c;
+		gb->cpu_reg.hl.bytes.h = gb->cpu_reg.bc.bytes.c;
 		break;
 
 	case 0x62: /* LD H, D */
-		gb->cpu_reg.h = gb->cpu_reg.d;
+		gb->cpu_reg.hl.bytes.h = gb->cpu_reg.de.bytes.d;
 		break;
 
 	case 0x63: /* LD H, E */
-		gb->cpu_reg.h = gb->cpu_reg.e;
+		gb->cpu_reg.hl.bytes.h = gb->cpu_reg.de.bytes.e;
 		break;
 
 	case 0x64: /* LD H, H */
 		break;
 
 	case 0x65: /* LD H, L */
-		gb->cpu_reg.h = gb->cpu_reg.l;
+		gb->cpu_reg.hl.bytes.h = gb->cpu_reg.hl.bytes.l;
 		break;
 
 	case 0x66: /* LD H, (HL) */
-		gb->cpu_reg.h = __gb_read(gb, gb->cpu_reg.hl);
+		gb->cpu_reg.hl.bytes.h = __gb_read(gb, gb->cpu_reg.hl.reg);
 		break;
 
 	case 0x67: /* LD H, A */
-		gb->cpu_reg.h = gb->cpu_reg.a;
+		gb->cpu_reg.hl.bytes.h = gb->cpu_reg.a;
 		break;
 
 	case 0x68: /* LD L, B */
-		gb->cpu_reg.l = gb->cpu_reg.b;
+		gb->cpu_reg.hl.bytes.l = gb->cpu_reg.bc.bytes.b;
 		break;
 
 	case 0x69: /* LD L, C */
-		gb->cpu_reg.l = gb->cpu_reg.c;
+		gb->cpu_reg.hl.bytes.l = gb->cpu_reg.bc.bytes.c;
 		break;
 
 	case 0x6A: /* LD L, D */
-		gb->cpu_reg.l = gb->cpu_reg.d;
+		gb->cpu_reg.hl.bytes.l = gb->cpu_reg.de.bytes.d;
 		break;
 
 	case 0x6B: /* LD L, E */
-		gb->cpu_reg.l = gb->cpu_reg.e;
+		gb->cpu_reg.hl.bytes.l = gb->cpu_reg.de.bytes.e;
 		break;
 
 	case 0x6C: /* LD L, H */
-		gb->cpu_reg.l = gb->cpu_reg.h;
+		gb->cpu_reg.hl.bytes.l = gb->cpu_reg.hl.bytes.h;
 		break;
 
 	case 0x6D: /* LD L, L */
 		break;
 
 	case 0x6E: /* LD L, (HL) */
-		gb->cpu_reg.l = __gb_read(gb, gb->cpu_reg.hl);
+		gb->cpu_reg.hl.bytes.l = __gb_read(gb, gb->cpu_reg.hl.reg);
 		break;
 
 	case 0x6F: /* LD L, A */
-		gb->cpu_reg.l = gb->cpu_reg.a;
+		gb->cpu_reg.hl.bytes.l = gb->cpu_reg.a;
 		break;
 
 	case 0x70: /* LD (HL), B */
-		__gb_write(gb, gb->cpu_reg.hl, gb->cpu_reg.b);
+		__gb_write(gb, gb->cpu_reg.hl.reg, gb->cpu_reg.bc.bytes.b);
 		break;
 
 	case 0x71: /* LD (HL), C */
-		__gb_write(gb, gb->cpu_reg.hl, gb->cpu_reg.c);
+		__gb_write(gb, gb->cpu_reg.hl.reg, gb->cpu_reg.bc.bytes.c);
 		break;
 
 	case 0x72: /* LD (HL), D */
-		__gb_write(gb, gb->cpu_reg.hl, gb->cpu_reg.d);
+		__gb_write(gb, gb->cpu_reg.hl.reg, gb->cpu_reg.de.bytes.d);
 		break;
 
 	case 0x73: /* LD (HL), E */
-		__gb_write(gb, gb->cpu_reg.hl, gb->cpu_reg.e);
+		__gb_write(gb, gb->cpu_reg.hl.reg, gb->cpu_reg.de.bytes.e);
 		break;
 
 	case 0x74: /* LD (HL), H */
-		__gb_write(gb, gb->cpu_reg.hl, gb->cpu_reg.h);
+		__gb_write(gb, gb->cpu_reg.hl.reg, gb->cpu_reg.hl.bytes.h);
 		break;
 
 	case 0x75: /* LD (HL), L */
-		__gb_write(gb, gb->cpu_reg.hl, gb->cpu_reg.l);
+		__gb_write(gb, gb->cpu_reg.hl.reg, gb->cpu_reg.hl.bytes.l);
 		break;
 
 	case 0x76: /* HALT */
+	{
+		int_fast16_t halt_cycles = INT_FAST16_MAX;
+
 		/* TODO: Emulate HALT bug? */
 		gb->gb_halt = 1;
-		if(gb->gb_reg.IE == 0)
+
+		if (gb->hram_io[IO_IE] == 0)
 		{
-			gb->direct.ended = 1;
-			return;
+			/* Return program counter where this halt forever state started. */
+			/* This may be intentional, but this is required to stop an infinite
+			 * loop. */
+			(gb->gb_error)(gb, GB_HALT_FOREVER, gb->cpu_reg.pc.reg - 1);
+			PGB_UNREACHABLE();
 		}
+
+		if(gb->hram_io[IO_SC] & SERIAL_SC_TX_START)
+		{
+			int serial_cycles = SERIAL_CYCLES -
+				gb->counter.serial_count;
+
+			if(serial_cycles < halt_cycles)
+				halt_cycles = serial_cycles;
+		}
+
+		if(gb->hram_io[IO_TAC] & IO_TAC_ENABLE_MASK)
+		{
+			int tac_cycles = TAC_CYCLES[gb->hram_io[IO_TAC] & IO_TAC_RATE_MASK] -
+				gb->counter.tima_count;
+
+			if(tac_cycles < halt_cycles)
+				halt_cycles = tac_cycles;
+		}
+
+		if((gb->hram_io[IO_LCDC] & LCDC_ENABLE) != 0)
+		{
+			int lcd_cycles;
+
+			if((gb->hram_io[IO_STAT] & STAT_MODE) == IO_STAT_MODE_SEARCH_OAM)
+			{
+				lcd_cycles = LCD_MODE_3_CYCLES -
+					gb->counter.lcd_count;
+			}
+			else if((gb->hram_io[IO_STAT] & STAT_MODE) == IO_STAT_MODE_HBLANK)
+			{
+				lcd_cycles = LCD_MODE_2_CYCLES -
+					gb->counter.lcd_count;
+			}
+			else
+			{
+				lcd_cycles =
+					LCD_LINE_CYCLES - gb->counter.lcd_count;
+			}
+
+			if(lcd_cycles < halt_cycles)
+				halt_cycles = lcd_cycles;
+		}
+
+		/* Some halt cycles may already be very high, so make sure we
+		 * don't underflow here. */
+		if(halt_cycles <= 0)
+			halt_cycles = 4;
+
+		inst_cycles = (uint_fast16_t)halt_cycles;
 		break;
+	}
 
 	case 0x77: /* LD (HL), A */
-		__gb_write(gb, gb->cpu_reg.hl, gb->cpu_reg.a);
+		__gb_write(gb, gb->cpu_reg.hl.reg, gb->cpu_reg.a);
 		break;
 
 	case 0x78: /* LD A, B */
-		gb->cpu_reg.a = gb->cpu_reg.b;
+		gb->cpu_reg.a = gb->cpu_reg.bc.bytes.b;
 		break;
 
 	case 0x79: /* LD A, C */
-		gb->cpu_reg.a = gb->cpu_reg.c;
+		gb->cpu_reg.a = gb->cpu_reg.bc.bytes.c;
 		break;
 
 	case 0x7A: /* LD A, D */
-		gb->cpu_reg.a = gb->cpu_reg.d;
+		gb->cpu_reg.a = gb->cpu_reg.de.bytes.d;
 		break;
 
 	case 0x7B: /* LD A, E */
-		gb->cpu_reg.a = gb->cpu_reg.e;
+		gb->cpu_reg.a = gb->cpu_reg.de.bytes.e;
 		break;
 
 	case 0x7C: /* LD A, H */
-		gb->cpu_reg.a = gb->cpu_reg.h;
+		gb->cpu_reg.a = gb->cpu_reg.hl.bytes.h;
 		break;
 
 	case 0x7D: /* LD A, L */
-		gb->cpu_reg.a = gb->cpu_reg.l;
+		gb->cpu_reg.a = gb->cpu_reg.hl.bytes.l;
 		break;
 
 	case 0x7E: /* LD A, (HL) */
-		gb->cpu_reg.a = __gb_read(gb, gb->cpu_reg.hl);
+		gb->cpu_reg.a = __gb_read(gb, gb->cpu_reg.hl.reg);
 		break;
 
 	case 0x7F: /* LD A, A */
 		break;
 
 	case 0x80: /* ADD A, B */
-	{
-		uint16_t temp = gb->cpu_reg.a + gb->cpu_reg.b;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 0;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.b ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		PGB_INSTR_ADC_R8(gb->cpu_reg.bc.bytes.b, 0);
 		break;
-	}
 
 	case 0x81: /* ADD A, C */
-	{
-		uint16_t temp = gb->cpu_reg.a + gb->cpu_reg.c;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 0;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.c ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		PGB_INSTR_ADC_R8(gb->cpu_reg.bc.bytes.c, 0);
 		break;
-	}
 
 	case 0x82: /* ADD A, D */
-	{
-		uint16_t temp = gb->cpu_reg.a + gb->cpu_reg.d;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 0;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.d ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		PGB_INSTR_ADC_R8(gb->cpu_reg.de.bytes.d, 0);
 		break;
-	}
 
 	case 0x83: /* ADD A, E */
-	{
-		uint16_t temp = gb->cpu_reg.a + gb->cpu_reg.e;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 0;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.e ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		PGB_INSTR_ADC_R8(gb->cpu_reg.de.bytes.e, 0);
 		break;
-	}
 
 	case 0x84: /* ADD A, H */
-	{
-		uint16_t temp = gb->cpu_reg.a + gb->cpu_reg.h;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 0;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.h ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		PGB_INSTR_ADC_R8(gb->cpu_reg.hl.bytes.h, 0);
 		break;
-	}
 
 	case 0x85: /* ADD A, L */
-	{
-		uint16_t temp = gb->cpu_reg.a + gb->cpu_reg.l;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 0;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.l ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		PGB_INSTR_ADC_R8(gb->cpu_reg.hl.bytes.l, 0);
 		break;
-	}
 
 	case 0x86: /* ADD A, (HL) */
 	{
-		uint8_t hl = __gb_read(gb, gb->cpu_reg.hl);
-		uint16_t temp = gb->cpu_reg.a + hl;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 0;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ hl ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		uint8_t val = __gb_read(gb, gb->cpu_reg.hl.reg);
+		PGB_INSTR_ADC_R8(val, 0);
 		break;
 	}
 
 	case 0x87: /* ADD A, A */
-	{
-		uint16_t temp = gb->cpu_reg.a + gb->cpu_reg.a;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 0;
-		gb->cpu_reg.f_bits.h = temp & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		PGB_INSTR_ADC_R8(gb->cpu_reg.a, 0);
 		break;
-	}
 
 	case 0x88: /* ADC A, B */
-	{
-		uint16_t temp = gb->cpu_reg.a + gb->cpu_reg.b + gb->cpu_reg.f_bits.c;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 0;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.b ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		PGB_INSTR_ADC_R8(gb->cpu_reg.bc.bytes.b, gb->cpu_reg.f_bits.c);
 		break;
-	}
 
 	case 0x89: /* ADC A, C */
-	{
-		uint16_t temp = gb->cpu_reg.a + gb->cpu_reg.c + gb->cpu_reg.f_bits.c;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 0;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.c ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		PGB_INSTR_ADC_R8(gb->cpu_reg.bc.bytes.c, gb->cpu_reg.f_bits.c);
 		break;
-	}
 
 	case 0x8A: /* ADC A, D */
-	{
-		uint16_t temp = gb->cpu_reg.a + gb->cpu_reg.d + gb->cpu_reg.f_bits.c;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 0;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.d ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		PGB_INSTR_ADC_R8(gb->cpu_reg.de.bytes.d, gb->cpu_reg.f_bits.c);
 		break;
-	}
 
 	case 0x8B: /* ADC A, E */
-	{
-		uint16_t temp = gb->cpu_reg.a + gb->cpu_reg.e + gb->cpu_reg.f_bits.c;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 0;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.e ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		PGB_INSTR_ADC_R8(gb->cpu_reg.de.bytes.e, gb->cpu_reg.f_bits.c);
 		break;
-	}
 
 	case 0x8C: /* ADC A, H */
-	{
-		uint16_t temp = gb->cpu_reg.a + gb->cpu_reg.h + gb->cpu_reg.f_bits.c;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 0;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.h ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		PGB_INSTR_ADC_R8(gb->cpu_reg.hl.bytes.h, gb->cpu_reg.f_bits.c);
 		break;
-	}
 
 	case 0x8D: /* ADC A, L */
-	{
-		uint16_t temp = gb->cpu_reg.a + gb->cpu_reg.l + gb->cpu_reg.f_bits.c;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 0;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.l ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		PGB_INSTR_ADC_R8(gb->cpu_reg.hl.bytes.l, gb->cpu_reg.f_bits.c);
 		break;
-	}
 
 	case 0x8E: /* ADC A, (HL) */
 	{
-		uint8_t val = __gb_read(gb, gb->cpu_reg.hl);
-		uint16_t temp = gb->cpu_reg.a + val + gb->cpu_reg.f_bits.c;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 0;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ val ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		uint8_t val = __gb_read(gb, gb->cpu_reg.hl.reg);
+		PGB_INSTR_ADC_R8(val, gb->cpu_reg.f_bits.c);
 		break;
 	}
 
 	case 0x8F: /* ADC A, A */
-	{
-		uint16_t temp = gb->cpu_reg.a + gb->cpu_reg.a + gb->cpu_reg.f_bits.c;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 0;
-		/* TODO: Optimisation here? */
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.a ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		PGB_INSTR_ADC_R8(gb->cpu_reg.a, gb->cpu_reg.f_bits.c);
 		break;
-	}
 
 	case 0x90: /* SUB B */
-	{
-		uint16_t temp = gb->cpu_reg.a - gb->cpu_reg.b;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.b ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		PGB_INSTR_SBC_R8(gb->cpu_reg.bc.bytes.b, 0);
 		break;
-	}
 
 	case 0x91: /* SUB C */
-	{
-		uint16_t temp = gb->cpu_reg.a - gb->cpu_reg.c;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.c ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		PGB_INSTR_SBC_R8(gb->cpu_reg.bc.bytes.c, 0);
 		break;
-	}
 
 	case 0x92: /* SUB D */
-	{
-		uint16_t temp = gb->cpu_reg.a - gb->cpu_reg.d;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.d ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		PGB_INSTR_SBC_R8(gb->cpu_reg.de.bytes.d, 0);
 		break;
-	}
 
 	case 0x93: /* SUB E */
-	{
-		uint16_t temp = gb->cpu_reg.a - gb->cpu_reg.e;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.e ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		PGB_INSTR_SBC_R8(gb->cpu_reg.de.bytes.e, 0);
 		break;
-	}
 
 	case 0x94: /* SUB H */
-	{
-		uint16_t temp = gb->cpu_reg.a - gb->cpu_reg.h;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.h ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		PGB_INSTR_SBC_R8(gb->cpu_reg.hl.bytes.h, 0);
 		break;
-	}
 
 	case 0x95: /* SUB L */
-	{
-		uint16_t temp = gb->cpu_reg.a - gb->cpu_reg.l;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.l ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		PGB_INSTR_SBC_R8(gb->cpu_reg.hl.bytes.l, 0);
 		break;
-	}
 
 	case 0x96: /* SUB (HL) */
 	{
-		uint8_t val = __gb_read(gb, gb->cpu_reg.hl);
-		uint16_t temp = gb->cpu_reg.a - val;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ val ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		uint8_t val = __gb_read(gb, gb->cpu_reg.hl.reg);
+		PGB_INSTR_SBC_R8(val, 0);
 		break;
 	}
 
@@ -2534,99 +2528,45 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0x98: /* SBC A, B */
-	{
-		uint16_t temp = gb->cpu_reg.a - gb->cpu_reg.b - gb->cpu_reg.f_bits.c;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.b ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		PGB_INSTR_SBC_R8(gb->cpu_reg.bc.bytes.b, gb->cpu_reg.f_bits.c);
 		break;
-	}
 
 	case 0x99: /* SBC A, C */
-	{
-		uint16_t temp = gb->cpu_reg.a - gb->cpu_reg.c - gb->cpu_reg.f_bits.c;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.c ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		PGB_INSTR_SBC_R8(gb->cpu_reg.bc.bytes.c, gb->cpu_reg.f_bits.c);
 		break;
-	}
 
 	case 0x9A: /* SBC A, D */
-	{
-		uint16_t temp = gb->cpu_reg.a - gb->cpu_reg.d - gb->cpu_reg.f_bits.c;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.d ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		PGB_INSTR_SBC_R8(gb->cpu_reg.de.bytes.d, gb->cpu_reg.f_bits.c);
 		break;
-	}
 
 	case 0x9B: /* SBC A, E */
-	{
-		uint16_t temp = gb->cpu_reg.a - gb->cpu_reg.e - gb->cpu_reg.f_bits.c;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.e ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		PGB_INSTR_SBC_R8(gb->cpu_reg.de.bytes.e, gb->cpu_reg.f_bits.c);
 		break;
-	}
 
 	case 0x9C: /* SBC A, H */
-	{
-		uint16_t temp = gb->cpu_reg.a - gb->cpu_reg.h - gb->cpu_reg.f_bits.c;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.h ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		PGB_INSTR_SBC_R8(gb->cpu_reg.hl.bytes.h, gb->cpu_reg.f_bits.c);
 		break;
-	}
 
 	case 0x9D: /* SBC A, L */
-	{
-		uint16_t temp = gb->cpu_reg.a - gb->cpu_reg.l - gb->cpu_reg.f_bits.c;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.l ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		PGB_INSTR_SBC_R8(gb->cpu_reg.hl.bytes.l, gb->cpu_reg.f_bits.c);
 		break;
-	}
 
 	case 0x9E: /* SBC A, (HL) */
 	{
-		uint8_t val = __gb_read(gb, gb->cpu_reg.hl);
-		uint16_t temp = gb->cpu_reg.a - val - gb->cpu_reg.f_bits.c;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ val ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp & 0xFF);
+		uint8_t val = __gb_read(gb, gb->cpu_reg.hl.reg);
+		PGB_INSTR_SBC_R8(val, gb->cpu_reg.f_bits.c);
 		break;
 	}
 
 	case 0x9F: /* SBC A, A */
 		gb->cpu_reg.a = gb->cpu_reg.f_bits.c ? 0xFF : 0x00;
-		gb->cpu_reg.f_bits.z = gb->cpu_reg.f_bits.c ? 0x00 : 0x01;
+		gb->cpu_reg.f_bits.z = !gb->cpu_reg.f_bits.c;
 		gb->cpu_reg.f_bits.n = 1;
 		gb->cpu_reg.f_bits.h = gb->cpu_reg.f_bits.c;
 		break;
 
 	case 0xA0: /* AND B */
-		gb->cpu_reg.a = gb->cpu_reg.a & gb->cpu_reg.b;
+		gb->cpu_reg.a = gb->cpu_reg.a & gb->cpu_reg.bc.bytes.b;
 		gb->cpu_reg.f_bits.z = (gb->cpu_reg.a == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h = 1;
@@ -2634,7 +2574,7 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0xA1: /* AND C */
-		gb->cpu_reg.a = gb->cpu_reg.a & gb->cpu_reg.c;
+		gb->cpu_reg.a = gb->cpu_reg.a & gb->cpu_reg.bc.bytes.c;
 		gb->cpu_reg.f_bits.z = (gb->cpu_reg.a == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h = 1;
@@ -2642,7 +2582,7 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0xA2: /* AND D */
-		gb->cpu_reg.a = gb->cpu_reg.a & gb->cpu_reg.d;
+		gb->cpu_reg.a = gb->cpu_reg.a & gb->cpu_reg.de.bytes.d;
 		gb->cpu_reg.f_bits.z = (gb->cpu_reg.a == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h = 1;
@@ -2650,7 +2590,7 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0xA3: /* AND E */
-		gb->cpu_reg.a = gb->cpu_reg.a & gb->cpu_reg.e;
+		gb->cpu_reg.a = gb->cpu_reg.a & gb->cpu_reg.de.bytes.e;
 		gb->cpu_reg.f_bits.z = (gb->cpu_reg.a == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h = 1;
@@ -2658,7 +2598,7 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0xA4: /* AND H */
-		gb->cpu_reg.a = gb->cpu_reg.a & gb->cpu_reg.h;
+		gb->cpu_reg.a = gb->cpu_reg.a & gb->cpu_reg.hl.bytes.h;
 		gb->cpu_reg.f_bits.z = (gb->cpu_reg.a == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h = 1;
@@ -2666,15 +2606,15 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0xA5: /* AND L */
-		gb->cpu_reg.a = gb->cpu_reg.a & gb->cpu_reg.l;
+		gb->cpu_reg.a = gb->cpu_reg.a & gb->cpu_reg.hl.bytes.l;
 		gb->cpu_reg.f_bits.z = (gb->cpu_reg.a == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h = 1;
 		gb->cpu_reg.f_bits.c = 0;
 		break;
 
-	case 0xA6: /* AND B */
-		gb->cpu_reg.a = gb->cpu_reg.a & __gb_read(gb, gb->cpu_reg.hl);
+	case 0xA6: /* AND (HL) */
+		gb->cpu_reg.a = gb->cpu_reg.a & __gb_read(gb, gb->cpu_reg.hl.reg);
 		gb->cpu_reg.f_bits.z = (gb->cpu_reg.a == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h = 1;
@@ -2689,7 +2629,7 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0xA8: /* XOR B */
-		gb->cpu_reg.a = gb->cpu_reg.a ^ gb->cpu_reg.b;
+		gb->cpu_reg.a = gb->cpu_reg.a ^ gb->cpu_reg.bc.bytes.b;
 		gb->cpu_reg.f_bits.z = (gb->cpu_reg.a == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h = 0;
@@ -2697,7 +2637,7 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0xA9: /* XOR C */
-		gb->cpu_reg.a = gb->cpu_reg.a ^ gb->cpu_reg.c;
+		gb->cpu_reg.a = gb->cpu_reg.a ^ gb->cpu_reg.bc.bytes.c;
 		gb->cpu_reg.f_bits.z = (gb->cpu_reg.a == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h = 0;
@@ -2705,7 +2645,7 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0xAA: /* XOR D */
-		gb->cpu_reg.a = gb->cpu_reg.a ^ gb->cpu_reg.d;
+		gb->cpu_reg.a = gb->cpu_reg.a ^ gb->cpu_reg.de.bytes.d;
 		gb->cpu_reg.f_bits.z = (gb->cpu_reg.a == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h = 0;
@@ -2713,7 +2653,7 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0xAB: /* XOR E */
-		gb->cpu_reg.a = gb->cpu_reg.a ^ gb->cpu_reg.e;
+		gb->cpu_reg.a = gb->cpu_reg.a ^ gb->cpu_reg.de.bytes.e;
 		gb->cpu_reg.f_bits.z = (gb->cpu_reg.a == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h = 0;
@@ -2721,7 +2661,7 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0xAC: /* XOR H */
-		gb->cpu_reg.a = gb->cpu_reg.a ^ gb->cpu_reg.h;
+		gb->cpu_reg.a = gb->cpu_reg.a ^ gb->cpu_reg.hl.bytes.h;
 		gb->cpu_reg.f_bits.z = (gb->cpu_reg.a == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h = 0;
@@ -2729,7 +2669,7 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0xAD: /* XOR L */
-		gb->cpu_reg.a = gb->cpu_reg.a ^ gb->cpu_reg.l;
+		gb->cpu_reg.a = gb->cpu_reg.a ^ gb->cpu_reg.hl.bytes.l;
 		gb->cpu_reg.f_bits.z = (gb->cpu_reg.a == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h = 0;
@@ -2737,7 +2677,7 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0xAE: /* XOR (HL) */
-		gb->cpu_reg.a = gb->cpu_reg.a ^ __gb_read(gb, gb->cpu_reg.hl);
+		gb->cpu_reg.a = gb->cpu_reg.a ^ __gb_read(gb, gb->cpu_reg.hl.reg);
 		gb->cpu_reg.f_bits.z = (gb->cpu_reg.a == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h = 0;
@@ -2753,7 +2693,7 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0xB0: /* OR B */
-		gb->cpu_reg.a = gb->cpu_reg.a | gb->cpu_reg.b;
+		gb->cpu_reg.a = gb->cpu_reg.a | gb->cpu_reg.bc.bytes.b;
 		gb->cpu_reg.f_bits.z = (gb->cpu_reg.a == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h = 0;
@@ -2761,7 +2701,7 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0xB1: /* OR C */
-		gb->cpu_reg.a = gb->cpu_reg.a | gb->cpu_reg.c;
+		gb->cpu_reg.a = gb->cpu_reg.a | gb->cpu_reg.bc.bytes.c;
 		gb->cpu_reg.f_bits.z = (gb->cpu_reg.a == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h = 0;
@@ -2769,7 +2709,7 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0xB2: /* OR D */
-		gb->cpu_reg.a = gb->cpu_reg.a | gb->cpu_reg.d;
+		gb->cpu_reg.a = gb->cpu_reg.a | gb->cpu_reg.de.bytes.d;
 		gb->cpu_reg.f_bits.z = (gb->cpu_reg.a == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h = 0;
@@ -2777,7 +2717,7 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0xB3: /* OR E */
-		gb->cpu_reg.a = gb->cpu_reg.a | gb->cpu_reg.e;
+		gb->cpu_reg.a = gb->cpu_reg.a | gb->cpu_reg.de.bytes.e;
 		gb->cpu_reg.f_bits.z = (gb->cpu_reg.a == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h = 0;
@@ -2785,7 +2725,7 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0xB4: /* OR H */
-		gb->cpu_reg.a = gb->cpu_reg.a | gb->cpu_reg.h;
+		gb->cpu_reg.a = gb->cpu_reg.a | gb->cpu_reg.hl.bytes.h;
 		gb->cpu_reg.f_bits.z = (gb->cpu_reg.a == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h = 0;
@@ -2793,7 +2733,7 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0xB5: /* OR L */
-		gb->cpu_reg.a = gb->cpu_reg.a | gb->cpu_reg.l;
+		gb->cpu_reg.a = gb->cpu_reg.a | gb->cpu_reg.hl.bytes.l;
 		gb->cpu_reg.f_bits.z = (gb->cpu_reg.a == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h = 0;
@@ -2801,7 +2741,7 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0xB6: /* OR (HL) */
-		gb->cpu_reg.a = gb->cpu_reg.a | __gb_read(gb, gb->cpu_reg.hl);
+		gb->cpu_reg.a = gb->cpu_reg.a | __gb_read(gb, gb->cpu_reg.hl.reg);
 		gb->cpu_reg.f_bits.z = (gb->cpu_reg.a == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h = 0;
@@ -2816,81 +2756,33 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0xB8: /* CP B */
-	{
-		uint16_t temp = gb->cpu_reg.a - gb->cpu_reg.b;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.b ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
+		PGB_INSTR_CP_R8(gb->cpu_reg.bc.bytes.b);
 		break;
-	}
 
 	case 0xB9: /* CP C */
-	{
-		uint16_t temp = gb->cpu_reg.a - gb->cpu_reg.c;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.c ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
+		PGB_INSTR_CP_R8(gb->cpu_reg.bc.bytes.c);
 		break;
-	}
 
 	case 0xBA: /* CP D */
-	{
-		uint16_t temp = gb->cpu_reg.a - gb->cpu_reg.d;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.d ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
+		PGB_INSTR_CP_R8(gb->cpu_reg.de.bytes.d);
 		break;
-	}
 
 	case 0xBB: /* CP E */
-	{
-		uint16_t temp = gb->cpu_reg.a - gb->cpu_reg.e;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.e ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
+		PGB_INSTR_CP_R8(gb->cpu_reg.de.bytes.e);
 		break;
-	}
 
 	case 0xBC: /* CP H */
-	{
-		uint16_t temp = gb->cpu_reg.a - gb->cpu_reg.h;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.h ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
+		PGB_INSTR_CP_R8(gb->cpu_reg.hl.bytes.h);
 		break;
-	}
 
 	case 0xBD: /* CP L */
-	{
-		uint16_t temp = gb->cpu_reg.a - gb->cpu_reg.l;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ gb->cpu_reg.l ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
+		PGB_INSTR_CP_R8(gb->cpu_reg.hl.bytes.l);
 		break;
-	}
 
-	/* TODO: Optimsation by combining similar opcode routines. */
-	case 0xBE: /* CP B */
+	case 0xBE: /* CP (HL) */
 	{
-		uint8_t val = __gb_read(gb, gb->cpu_reg.hl);
-		uint16_t temp = gb->cpu_reg.a - val;
-		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ val ^ temp) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp & 0xFF00) ? 1 : 0;
+		uint8_t val = __gb_read(gb, gb->cpu_reg.hl.reg);
+		PGB_INSTR_CP_R8(val);
 		break;
 	}
 
@@ -2904,108 +2796,106 @@ void __gb_step_cpu(struct gb_s *gb)
 	case 0xC0: /* RET NZ */
 		if(!gb->cpu_reg.f_bits.z)
 		{
-			gb->cpu_reg.pc = __gb_read(gb, gb->cpu_reg.sp++);
-			gb->cpu_reg.pc |= __gb_read(gb, gb->cpu_reg.sp++) << 8;
+			gb->cpu_reg.pc.bytes.c = __gb_read(gb, gb->cpu_reg.sp.reg++);
+			gb->cpu_reg.pc.bytes.p = __gb_read(gb, gb->cpu_reg.sp.reg++);
 			inst_cycles += 12;
 		}
 
 		break;
 
 	case 0xC1: /* POP BC */
-		gb->cpu_reg.c = __gb_read(gb, gb->cpu_reg.sp++);
-		gb->cpu_reg.b = __gb_read(gb, gb->cpu_reg.sp++);
+		gb->cpu_reg.bc.bytes.c = __gb_read(gb, gb->cpu_reg.sp.reg++);
+		gb->cpu_reg.bc.bytes.b = __gb_read(gb, gb->cpu_reg.sp.reg++);
 		break;
 
 	case 0xC2: /* JP NZ, imm */
 		if(!gb->cpu_reg.f_bits.z)
 		{
-			uint16_t temp = __gb_read(gb, gb->cpu_reg.pc++);
-			temp |= __gb_read(gb, gb->cpu_reg.pc++) << 8;
-			gb->cpu_reg.pc = temp;
+			uint8_t p, c;
+			c = __gb_read(gb, gb->cpu_reg.pc.reg++);
+			p = __gb_read(gb, gb->cpu_reg.pc.reg);
+			gb->cpu_reg.pc.bytes.c = c;
+			gb->cpu_reg.pc.bytes.p = p;
 			inst_cycles += 4;
 		}
 		else
-			gb->cpu_reg.pc += 2;
+			gb->cpu_reg.pc.reg += 2;
 
 		break;
 
 	case 0xC3: /* JP imm */
 	{
-		uint16_t temp = __gb_read(gb, gb->cpu_reg.pc++);
-		temp |= __gb_read(gb, gb->cpu_reg.pc) << 8;
-		gb->cpu_reg.pc = temp;
+		uint8_t p, c;
+		c = __gb_read(gb, gb->cpu_reg.pc.reg++);
+		p = __gb_read(gb, gb->cpu_reg.pc.reg);
+		gb->cpu_reg.pc.bytes.c = c;
+		gb->cpu_reg.pc.bytes.p = p;
 		break;
 	}
 
 	case 0xC4: /* CALL NZ imm */
 		if(!gb->cpu_reg.f_bits.z)
 		{
-			uint16_t temp = __gb_read(gb, gb->cpu_reg.pc++);
-			temp |= __gb_read(gb, gb->cpu_reg.pc++) << 8;
-			__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc >> 8);
-			__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc & 0xFF);
-			gb->cpu_reg.pc = temp;
+			uint8_t p, c;
+			c = __gb_read(gb, gb->cpu_reg.pc.reg++);
+			p = __gb_read(gb, gb->cpu_reg.pc.reg++);
+			__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.p);
+			__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.c);
+			gb->cpu_reg.pc.bytes.c = c;
+			gb->cpu_reg.pc.bytes.p = p;
 			inst_cycles += 12;
 		}
 		else
-			gb->cpu_reg.pc += 2;
+			gb->cpu_reg.pc.reg += 2;
 
 		break;
 
 	case 0xC5: /* PUSH BC */
-		__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.b);
-		__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.c);
+		__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.bc.bytes.b);
+		__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.bc.bytes.c);
 		break;
 
 	case 0xC6: /* ADD A, imm */
 	{
-		/* Taken from SameBoy, which is released under MIT Licence. */
-		uint8_t value = __gb_read(gb, gb->cpu_reg.pc++);
-		uint16_t calc = gb->cpu_reg.a + value;
-		gb->cpu_reg.f_bits.z = ((uint8_t)calc == 0) ? 1 : 0;
-		gb->cpu_reg.f_bits.h =
-			((gb->cpu_reg.a & 0xF) + (value & 0xF) > 0x0F) ? 1 : 0;
-		gb->cpu_reg.f_bits.c = calc > 0xFF ? 1 : 0;
-		gb->cpu_reg.f_bits.n = 0;
-		gb->cpu_reg.a = (uint8_t)calc;
+		uint8_t val = __gb_read(gb, gb->cpu_reg.pc.reg++);
+		PGB_INSTR_ADC_R8(val, 0);
 		break;
 	}
 
 	case 0xC7: /* RST 0x0000 */
-		__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc >> 8);
-		__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc & 0xFF);
-		gb->cpu_reg.pc = 0x0000;
+		__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.p);
+		__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.c);
+		gb->cpu_reg.pc.reg = 0x0000;
 		break;
 
 	case 0xC8: /* RET Z */
 		if(gb->cpu_reg.f_bits.z)
 		{
-			uint16_t temp = __gb_read(gb, gb->cpu_reg.sp++);
-			temp |= __gb_read(gb, gb->cpu_reg.sp++) << 8;
-			gb->cpu_reg.pc = temp;
+			gb->cpu_reg.pc.bytes.c = __gb_read(gb, gb->cpu_reg.sp.reg++);
+			gb->cpu_reg.pc.bytes.p = __gb_read(gb, gb->cpu_reg.sp.reg++);
 			inst_cycles += 12;
 		}
-
 		break;
 
 	case 0xC9: /* RET */
 	{
-		uint16_t temp = __gb_read(gb, gb->cpu_reg.sp++);
-		temp |= __gb_read(gb, gb->cpu_reg.sp++) << 8;
-		gb->cpu_reg.pc = temp;
+		gb->cpu_reg.pc.bytes.c = __gb_read(gb, gb->cpu_reg.sp.reg++);
+		gb->cpu_reg.pc.bytes.p = __gb_read(gb, gb->cpu_reg.sp.reg++);
 		break;
 	}
 
 	case 0xCA: /* JP Z, imm */
 		if(gb->cpu_reg.f_bits.z)
 		{
-			uint16_t temp = __gb_read(gb, gb->cpu_reg.pc++);
-			temp |= __gb_read(gb, gb->cpu_reg.pc++) << 8;
-			gb->cpu_reg.pc = temp;
+			uint8_t p, c;
+			c = __gb_read(gb, gb->cpu_reg.pc.reg++);
+			p = __gb_read(gb, gb->cpu_reg.pc.reg);
+			gb->cpu_reg.pc.bytes.c = c;
+			gb->cpu_reg.pc.bytes.p = p;
 			inst_cycles += 4;
 		}
 		else
-			gb->cpu_reg.pc += 2;
+			gb->cpu_reg.pc.reg += 2;
 
 		break;
 
@@ -3016,103 +2906,100 @@ void __gb_step_cpu(struct gb_s *gb)
 	case 0xCC: /* CALL Z, imm */
 		if(gb->cpu_reg.f_bits.z)
 		{
-			uint16_t temp = __gb_read(gb, gb->cpu_reg.pc++);
-			temp |= __gb_read(gb, gb->cpu_reg.pc++) << 8;
-			__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc >> 8);
-			__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc & 0xFF);
-			gb->cpu_reg.pc = temp;
+			uint8_t p, c;
+			c = __gb_read(gb, gb->cpu_reg.pc.reg++);
+			p = __gb_read(gb, gb->cpu_reg.pc.reg++);
+			__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.p);
+			__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.c);
+			gb->cpu_reg.pc.bytes.c = c;
+			gb->cpu_reg.pc.bytes.p = p;
 			inst_cycles += 12;
 		}
 		else
-			gb->cpu_reg.pc += 2;
+			gb->cpu_reg.pc.reg += 2;
 
 		break;
 
 	case 0xCD: /* CALL imm */
 	{
-		uint16_t addr = __gb_read(gb, gb->cpu_reg.pc++);
-		addr |= __gb_read(gb, gb->cpu_reg.pc++) << 8;
-		__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc >> 8);
-		__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc & 0xFF);
-		gb->cpu_reg.pc = addr;
+		uint8_t p, c;
+		c = __gb_read(gb, gb->cpu_reg.pc.reg++);
+		p = __gb_read(gb, gb->cpu_reg.pc.reg++);
+		__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.p);
+		__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.c);
+		gb->cpu_reg.pc.bytes.c = c;
+		gb->cpu_reg.pc.bytes.p = p;
 	}
 	break;
 
 	case 0xCE: /* ADC A, imm */
 	{
-		uint8_t value, a, carry;
-		value = __gb_read(gb, gb->cpu_reg.pc++);
-		a = gb->cpu_reg.a;
-		carry = gb->cpu_reg.f_bits.c;
-		gb->cpu_reg.a = a + value + carry;
-
-		gb->cpu_reg.f_bits.z = gb->cpu_reg.a == 0 ? 1 : 0;
-		gb->cpu_reg.f_bits.h =
-			((a & 0xF) + (value & 0xF) + carry > 0x0F) ? 1 : 0;
-		gb->cpu_reg.f_bits.c =
-			(((uint16_t) a) + ((uint16_t) value) + carry > 0xFF) ? 1 : 0;
-		gb->cpu_reg.f_bits.n = 0;
+		uint8_t val = __gb_read(gb, gb->cpu_reg.pc.reg++);
+		PGB_INSTR_ADC_R8(val, gb->cpu_reg.f_bits.c);
 		break;
 	}
 
 	case 0xCF: /* RST 0x0008 */
-		__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc >> 8);
-		__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc & 0xFF);
-		gb->cpu_reg.pc = 0x0008;
+		__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.p);
+		__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.c);
+		gb->cpu_reg.pc.reg = 0x0008;
 		break;
 
 	case 0xD0: /* RET NC */
 		if(!gb->cpu_reg.f_bits.c)
 		{
-			uint16_t temp = __gb_read(gb, gb->cpu_reg.sp++);
-			temp |= __gb_read(gb, gb->cpu_reg.sp++) << 8;
-			gb->cpu_reg.pc = temp;
+			gb->cpu_reg.pc.bytes.c = __gb_read(gb, gb->cpu_reg.sp.reg++);
+			gb->cpu_reg.pc.bytes.p = __gb_read(gb, gb->cpu_reg.sp.reg++);
 			inst_cycles += 12;
 		}
 
 		break;
 
 	case 0xD1: /* POP DE */
-		gb->cpu_reg.e = __gb_read(gb, gb->cpu_reg.sp++);
-		gb->cpu_reg.d = __gb_read(gb, gb->cpu_reg.sp++);
+		gb->cpu_reg.de.bytes.e = __gb_read(gb, gb->cpu_reg.sp.reg++);
+		gb->cpu_reg.de.bytes.d = __gb_read(gb, gb->cpu_reg.sp.reg++);
 		break;
 
 	case 0xD2: /* JP NC, imm */
 		if(!gb->cpu_reg.f_bits.c)
 		{
-			uint16_t temp =  __gb_read(gb, gb->cpu_reg.pc++);
-			temp |=  __gb_read(gb, gb->cpu_reg.pc++) << 8;
-			gb->cpu_reg.pc = temp;
+			uint8_t p, c;
+			c = __gb_read(gb, gb->cpu_reg.pc.reg++);
+			p = __gb_read(gb, gb->cpu_reg.pc.reg);
+			gb->cpu_reg.pc.bytes.c = c;
+			gb->cpu_reg.pc.bytes.p = p;
 			inst_cycles += 4;
 		}
 		else
-			gb->cpu_reg.pc += 2;
+			gb->cpu_reg.pc.reg += 2;
 
 		break;
 
 	case 0xD4: /* CALL NC, imm */
 		if(!gb->cpu_reg.f_bits.c)
 		{
-			uint16_t temp = __gb_read(gb, gb->cpu_reg.pc++);
-			temp |= __gb_read(gb, gb->cpu_reg.pc++) << 8;
-			__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc >> 8);
-			__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc & 0xFF);
-			gb->cpu_reg.pc = temp;
+			uint8_t p, c;
+			c = __gb_read(gb, gb->cpu_reg.pc.reg++);
+			p = __gb_read(gb, gb->cpu_reg.pc.reg++);
+			__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.p);
+			__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.c);
+			gb->cpu_reg.pc.bytes.c = c;
+			gb->cpu_reg.pc.bytes.p = p;
 			inst_cycles += 12;
 		}
 		else
-			gb->cpu_reg.pc += 2;
+			gb->cpu_reg.pc.reg += 2;
 
 		break;
 
 	case 0xD5: /* PUSH DE */
-		__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.d);
-		__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.e);
+		__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.de.bytes.d);
+		__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.de.bytes.e);
 		break;
 
 	case 0xD6: /* SUB imm */
 	{
-		uint8_t val = __gb_read(gb, gb->cpu_reg.pc++);
+		uint8_t val = __gb_read(gb, gb->cpu_reg.pc.reg++);
 		uint16_t temp = gb->cpu_reg.a - val;
 		gb->cpu_reg.f_bits.z = ((temp & 0xFF) == 0x00);
 		gb->cpu_reg.f_bits.n = 1;
@@ -3124,17 +3011,16 @@ void __gb_step_cpu(struct gb_s *gb)
 	}
 
 	case 0xD7: /* RST 0x0010 */
-		__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc >> 8);
-		__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc & 0xFF);
-		gb->cpu_reg.pc = 0x0010;
+		__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.p);
+		__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.c);
+		gb->cpu_reg.pc.reg = 0x0010;
 		break;
 
 	case 0xD8: /* RET C */
 		if(gb->cpu_reg.f_bits.c)
 		{
-			uint16_t temp = __gb_read(gb, gb->cpu_reg.sp++);
-			temp |= __gb_read(gb, gb->cpu_reg.sp++) << 8;
-			gb->cpu_reg.pc = temp;
+			gb->cpu_reg.pc.bytes.c = __gb_read(gb, gb->cpu_reg.sp.reg++);
+			gb->cpu_reg.pc.bytes.p = __gb_read(gb, gb->cpu_reg.sp.reg++);
 			inst_cycles += 12;
 		}
 
@@ -3142,9 +3028,8 @@ void __gb_step_cpu(struct gb_s *gb)
 
 	case 0xD9: /* RETI */
 	{
-		uint16_t temp = __gb_read(gb, gb->cpu_reg.sp++);
-		temp |= __gb_read(gb, gb->cpu_reg.sp++) << 8;
-		gb->cpu_reg.pc = temp;
+		gb->cpu_reg.pc.bytes.c = __gb_read(gb, gb->cpu_reg.sp.reg++);
+		gb->cpu_reg.pc.bytes.p = __gb_read(gb, gb->cpu_reg.sp.reg++);
 		gb->gb_ime = 1;
 	}
 	break;
@@ -3152,72 +3037,70 @@ void __gb_step_cpu(struct gb_s *gb)
 	case 0xDA: /* JP C, imm */
 		if(gb->cpu_reg.f_bits.c)
 		{
-			uint16_t addr = __gb_read(gb, gb->cpu_reg.pc++);
-			addr |= __gb_read(gb, gb->cpu_reg.pc++) << 8;
-			gb->cpu_reg.pc = addr;
+			uint8_t p, c;
+			c = __gb_read(gb, gb->cpu_reg.pc.reg++);
+			p = __gb_read(gb, gb->cpu_reg.pc.reg);
+			gb->cpu_reg.pc.bytes.c = c;
+			gb->cpu_reg.pc.bytes.p = p;
 			inst_cycles += 4;
 		}
 		else
-			gb->cpu_reg.pc += 2;
+			gb->cpu_reg.pc.reg += 2;
 
 		break;
 
 	case 0xDC: /* CALL C, imm */
 		if(gb->cpu_reg.f_bits.c)
 		{
-			uint16_t temp = __gb_read(gb, gb->cpu_reg.pc++);
-			temp |= __gb_read(gb, gb->cpu_reg.pc++) << 8;
-			__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc >> 8);
-			__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc & 0xFF);
-			gb->cpu_reg.pc = temp;
+			uint8_t p, c;
+			c = __gb_read(gb, gb->cpu_reg.pc.reg++);
+			p = __gb_read(gb, gb->cpu_reg.pc.reg++);
+			__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.p);
+			__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.c);
+			gb->cpu_reg.pc.bytes.c = c;
+			gb->cpu_reg.pc.bytes.p = p;
 			inst_cycles += 12;
 		}
 		else
-			gb->cpu_reg.pc += 2;
+			gb->cpu_reg.pc.reg += 2;
 
 		break;
 
 	case 0xDE: /* SBC A, imm */
 	{
-		uint8_t temp_8 = __gb_read(gb, gb->cpu_reg.pc++);
-		uint16_t temp_16 = gb->cpu_reg.a - temp_8 - gb->cpu_reg.f_bits.c;
-		gb->cpu_reg.f_bits.z = ((temp_16 & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h =
-			(gb->cpu_reg.a ^ temp_8 ^ temp_16) & 0x10 ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp_16 & 0xFF00) ? 1 : 0;
-		gb->cpu_reg.a = (temp_16 & 0xFF);
+		uint8_t val = __gb_read(gb, gb->cpu_reg.pc.reg++);
+		PGB_INSTR_SBC_R8(val, gb->cpu_reg.f_bits.c);
 		break;
 	}
 
 	case 0xDF: /* RST 0x0018 */
-		__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc >> 8);
-		__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc & 0xFF);
-		gb->cpu_reg.pc = 0x0018;
+		__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.p);
+		__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.c);
+		gb->cpu_reg.pc.reg = 0x0018;
 		break;
 
 	case 0xE0: /* LD (0xFF00+imm), A */
-		__gb_write(gb, 0xFF00 | __gb_read(gb, gb->cpu_reg.pc++),
+		__gb_write(gb, 0xFF00 | __gb_read(gb, gb->cpu_reg.pc.reg++),
 			   gb->cpu_reg.a);
 		break;
 
 	case 0xE1: /* POP HL */
-		gb->cpu_reg.l = __gb_read(gb, gb->cpu_reg.sp++);
-		gb->cpu_reg.h = __gb_read(gb, gb->cpu_reg.sp++);
+		gb->cpu_reg.hl.bytes.l = __gb_read(gb, gb->cpu_reg.sp.reg++);
+		gb->cpu_reg.hl.bytes.h = __gb_read(gb, gb->cpu_reg.sp.reg++);
 		break;
 
 	case 0xE2: /* LD (C), A */
-		__gb_write(gb, 0xFF00 | gb->cpu_reg.c, gb->cpu_reg.a);
+		__gb_write(gb, 0xFF00 | gb->cpu_reg.bc.bytes.c, gb->cpu_reg.a);
 		break;
 
 	case 0xE5: /* PUSH HL */
-		__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.h);
-		__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.l);
+		__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.hl.bytes.h);
+		__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.hl.bytes.l);
 		break;
 
 	case 0xE6: /* AND imm */
 		/* TODO: Optimisation? */
-		gb->cpu_reg.a = gb->cpu_reg.a & __gb_read(gb, gb->cpu_reg.pc++);
+		gb->cpu_reg.a = gb->cpu_reg.a & __gb_read(gb, gb->cpu_reg.pc.reg++);
 		gb->cpu_reg.f_bits.z = (gb->cpu_reg.a == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h = 1;
@@ -3225,37 +3108,39 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0xE7: /* RST 0x0020 */
-		__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc >> 8);
-		__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc & 0xFF);
-		gb->cpu_reg.pc = 0x0020;
+		__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.p);
+		__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.c);
+		gb->cpu_reg.pc.reg = 0x0020;
 		break;
 
 	case 0xE8: /* ADD SP, imm */
 	{
-		int8_t offset = (int8_t) __gb_read(gb, gb->cpu_reg.pc++);
-		/* TODO: Move flag assignments for optimisation. */
+		int8_t offset = (int8_t) __gb_read(gb, gb->cpu_reg.pc.reg++);
 		gb->cpu_reg.f_bits.z = 0;
 		gb->cpu_reg.f_bits.n = 0;
-		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.sp & 0xF) + (offset & 0xF) > 0xF) ? 1 : 0;
-		gb->cpu_reg.f_bits.c = ((gb->cpu_reg.sp & 0xFF) + (offset & 0xFF) > 0xFF);
-		gb->cpu_reg.sp += offset;
+		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.sp.reg & 0xF) + (offset & 0xF) > 0xF) ? 1 : 0;
+		gb->cpu_reg.f_bits.c = ((gb->cpu_reg.sp.reg & 0xFF) + (offset & 0xFF) > 0xFF);
+		gb->cpu_reg.sp.reg += offset;
 		break;
 	}
 
 	case 0xE9: /* JP (HL) */
-		gb->cpu_reg.pc = gb->cpu_reg.hl;
+		gb->cpu_reg.pc.reg = gb->cpu_reg.hl.reg;
 		break;
 
 	case 0xEA: /* LD (imm), A */
 	{
-		uint16_t addr = __gb_read(gb, gb->cpu_reg.pc++);
-		addr |= __gb_read(gb, gb->cpu_reg.pc++) << 8;
+		uint8_t h, l;
+		uint16_t addr;
+		l = __gb_read(gb, gb->cpu_reg.pc.reg++);
+		h = __gb_read(gb, gb->cpu_reg.pc.reg++);
+		addr = PEANUT_GB_U8_TO_U16(h, l);
 		__gb_write(gb, addr, gb->cpu_reg.a);
 		break;
 	}
 
 	case 0xEE: /* XOR imm */
-		gb->cpu_reg.a = gb->cpu_reg.a ^ __gb_read(gb, gb->cpu_reg.pc++);
+		gb->cpu_reg.a = gb->cpu_reg.a ^ __gb_read(gb, gb->cpu_reg.pc.reg++);
 		gb->cpu_reg.f_bits.z = (gb->cpu_reg.a == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h = 0;
@@ -3263,29 +3148,29 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0xEF: /* RST 0x0028 */
-		__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc >> 8);
-		__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc & 0xFF);
-		gb->cpu_reg.pc = 0x0028;
+		__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.p);
+		__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.c);
+		gb->cpu_reg.pc.reg = 0x0028;
 		break;
 
 	case 0xF0: /* LD A, (0xFF00+imm) */
 		gb->cpu_reg.a =
-			__gb_read(gb, 0xFF00 | __gb_read(gb, gb->cpu_reg.pc++));
+			__gb_read(gb, 0xFF00 | __gb_read(gb, gb->cpu_reg.pc.reg++));
 		break;
 
 	case 0xF1: /* POP AF */
 	{
-		uint8_t temp_8 = __gb_read(gb, gb->cpu_reg.sp++);
+		uint8_t temp_8 = __gb_read(gb, gb->cpu_reg.sp.reg++);
 		gb->cpu_reg.f_bits.z = (temp_8 >> 7) & 1;
 		gb->cpu_reg.f_bits.n = (temp_8 >> 6) & 1;
 		gb->cpu_reg.f_bits.h = (temp_8 >> 5) & 1;
 		gb->cpu_reg.f_bits.c = (temp_8 >> 4) & 1;
-		gb->cpu_reg.a = __gb_read(gb, gb->cpu_reg.sp++);
+		gb->cpu_reg.a = __gb_read(gb, gb->cpu_reg.sp.reg++);
 		break;
 	}
 
 	case 0xF2: /* LD A, (C) */
-		gb->cpu_reg.a = __gb_read(gb, 0xFF00 | gb->cpu_reg.c);
+		gb->cpu_reg.a = __gb_read(gb, 0xFF00 | gb->cpu_reg.bc.bytes.c);
 		break;
 
 	case 0xF3: /* DI */
@@ -3293,14 +3178,14 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0xF5: /* PUSH AF */
-		__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.a);
-		__gb_write(gb, --gb->cpu_reg.sp,
+		__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.a);
+		__gb_write(gb, --gb->cpu_reg.sp.reg,
 			   gb->cpu_reg.f_bits.z << 7 | gb->cpu_reg.f_bits.n << 6 |
 			   gb->cpu_reg.f_bits.h << 5 | gb->cpu_reg.f_bits.c << 4);
 		break;
 
 	case 0xF6: /* OR imm */
-		gb->cpu_reg.a = gb->cpu_reg.a | __gb_read(gb, gb->cpu_reg.pc++);
+		gb->cpu_reg.a = gb->cpu_reg.a | __gb_read(gb, gb->cpu_reg.pc.reg++);
 		gb->cpu_reg.f_bits.z = (gb->cpu_reg.a == 0x00);
 		gb->cpu_reg.f_bits.n = 0;
 		gb->cpu_reg.f_bits.h = 0;
@@ -3308,32 +3193,35 @@ void __gb_step_cpu(struct gb_s *gb)
 		break;
 
 	case 0xF7: /* PUSH AF */
-		__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc >> 8);
-		__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc & 0xFF);
-		gb->cpu_reg.pc = 0x0030;
+		__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.p);
+		__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.c);
+		gb->cpu_reg.pc.reg = 0x0030;
 		break;
 
 	case 0xF8: /* LD HL, SP+/-imm */
 	{
 		/* Taken from SameBoy, which is released under MIT Licence. */
-		int8_t offset = (int8_t) __gb_read(gb, gb->cpu_reg.pc++);
-		gb->cpu_reg.hl = gb->cpu_reg.sp + offset;
+		int8_t offset = (int8_t) __gb_read(gb, gb->cpu_reg.pc.reg++);
+		gb->cpu_reg.hl.reg = gb->cpu_reg.sp.reg + offset;
 		gb->cpu_reg.f_bits.z = 0;
 		gb->cpu_reg.f_bits.n = 0;
-		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.sp & 0xF) + (offset & 0xF) > 0xF) ? 1 : 0;
-		gb->cpu_reg.f_bits.c = ((gb->cpu_reg.sp & 0xFF) + (offset & 0xFF) > 0xFF) ? 1 :
+		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.sp.reg & 0xF) + (offset & 0xF) > 0xF) ? 1 : 0;
+		gb->cpu_reg.f_bits.c = ((gb->cpu_reg.sp.reg & 0xFF) + (offset & 0xFF) > 0xFF) ? 1 :
 				       0;
 		break;
 	}
 
 	case 0xF9: /* LD SP, HL */
-		gb->cpu_reg.sp = gb->cpu_reg.hl;
+		gb->cpu_reg.sp.reg = gb->cpu_reg.hl.reg;
 		break;
 
 	case 0xFA: /* LD A, (imm) */
 	{
-		uint16_t addr = __gb_read(gb, gb->cpu_reg.pc++);
-		addr |= __gb_read(gb, gb->cpu_reg.pc++) << 8;
+		uint8_t h, l;
+		uint16_t addr;
+		l = __gb_read(gb, gb->cpu_reg.pc.reg++);
+		h = __gb_read(gb, gb->cpu_reg.pc.reg++);
+		addr = PEANUT_GB_U8_TO_U16(h, l);
 		gb->cpu_reg.a = __gb_read(gb, addr);
 		break;
 	}
@@ -3344,200 +3232,218 @@ void __gb_step_cpu(struct gb_s *gb)
 
 	case 0xFE: /* CP imm */
 	{
-		uint8_t temp_8 = __gb_read(gb, gb->cpu_reg.pc++);
-		uint16_t temp_16 = gb->cpu_reg.a - temp_8;
-		gb->cpu_reg.f_bits.z = ((temp_16 & 0xFF) == 0x00);
-		gb->cpu_reg.f_bits.n = 1;
-		gb->cpu_reg.f_bits.h = ((gb->cpu_reg.a ^ temp_8 ^ temp_16) & 0x10) ? 1 : 0;
-		gb->cpu_reg.f_bits.c = (temp_16 & 0xFF00) ? 1 : 0;
+		uint8_t val = __gb_read(gb, gb->cpu_reg.pc.reg++);
+		PGB_INSTR_CP_R8(val);
 		break;
 	}
 
 	case 0xFF: /* RST 0x0038 */
-		__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc >> 8);
-		__gb_write(gb, --gb->cpu_reg.sp, gb->cpu_reg.pc & 0xFF);
-		gb->cpu_reg.pc = 0x0038;
+		__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.p);
+		__gb_write(gb, --gb->cpu_reg.sp.reg, gb->cpu_reg.pc.bytes.c);
+		gb->cpu_reg.pc.reg = 0x0038;
 		break;
 
 	default:
-		(gb->gb_error)(gb, GB_INVALID_OPCODE, opcode);
+		/* Return address where invlid opcode that was read. */
+		(gb->gb_error)(gb, GB_INVALID_OPCODE, gb->cpu_reg.pc.reg - 1);
+		PGB_UNREACHABLE();
 	}
 
-	/* DIV register timing */
-	gb->counter.div_count += inst_cycles;
-
-	if(gb->counter.div_count >= DIV_CYCLES)
+	do
 	{
-		gb->gb_reg.DIV++;
-		gb->counter.div_count -= DIV_CYCLES;
-	}
+		/* DIV register timing */
+		gb->counter.div_count += inst_cycles;
 
-	/* Check serial transmission. */
-	if(HEDLEY_UNLIKELY(gb->gb_reg.SC & SERIAL_SC_TX_START))
-	{
-		/* If new transfer, call TX function. */
-		if(gb->counter.serial_count == 0 && gb->gb_serial_tx != NULL)
-			(gb->gb_serial_tx)(gb, gb->gb_reg.SB);
-
-		gb->counter.serial_count += inst_cycles;
-
-		/* If it's time to receive byte, call RX function. */
-		if(gb->counter.serial_count >= SERIAL_CYCLES)
+		while(gb->counter.div_count >= DIV_CYCLES)
 		{
-			/* If RX can be done, do it. */
-			/* If RX failed, do not change SB if using external
-			 * clock, or set to 0xFF if using internal clock. */
-			uint8_t rx;
+			gb->hram_io[IO_DIV]++;
+			gb->counter.div_count -= DIV_CYCLES;
+		}
 
-			if(gb->gb_serial_rx != NULL &&
-				(gb->gb_serial_rx(gb, &rx) ==
-					 GB_SERIAL_RX_SUCCESS))
+		/* Check serial transmission. */
+		if(gb->hram_io[IO_SC] & SERIAL_SC_TX_START)
+		{
+			/* If new transfer, call TX function. */
+			if(gb->counter.serial_count == 0 &&
+				gb->gb_serial_tx != NULL)
+				(gb->gb_serial_tx)(gb, gb->hram_io[IO_SB]);
+
+			gb->counter.serial_count += inst_cycles;
+
+			/* If it's time to receive byte, call RX function. */
+			if(gb->counter.serial_count >= SERIAL_CYCLES)
 			{
-				gb->gb_reg.SB = rx;
+				/* If RX can be done, do it. */
+				/* If RX failed, do not change SB if using external
+				 * clock, or set to 0xFF if using internal clock. */
+				uint8_t rx;
 
-				/* Inform game of serial TX/RX completion. */
-				gb->gb_reg.SC &= 0x01;
-				gb->gb_reg.IF |= SERIAL_INTR;
+				if(gb->gb_serial_rx != NULL &&
+					(gb->gb_serial_rx(gb, &rx) ==
+						GB_SERIAL_RX_SUCCESS))
+				{
+					gb->hram_io[IO_SB] = rx;
+
+					/* Inform game of serial TX/RX completion. */
+					gb->hram_io[IO_SC] &= 0x01;
+					gb->hram_io[IO_IF] |= SERIAL_INTR;
+				}
+				else if(gb->hram_io[IO_SC] & SERIAL_SC_CLOCK_SRC)
+				{
+					/* If using internal clock, and console is not
+					 * attached to any external peripheral, shifted
+					 * bits are replaced with logic 1. */
+					gb->hram_io[IO_SB] = 0xFF;
+
+					/* Inform game of serial TX/RX completion. */
+					gb->hram_io[IO_SC] &= 0x01;
+					gb->hram_io[IO_IF] |= SERIAL_INTR;
+				}
+				else
+				{
+					/* If using external clock, and console is not
+					 * attached to any external peripheral, bits are
+					 * not shifted, so SB is not modified. */
+				}
+
+				gb->counter.serial_count = 0;
 			}
-			else if(gb->gb_reg.SC & SERIAL_SC_CLOCK_SRC)
-			{
-				/* If using internal clock, and console is not
-				 * attached to any external peripheral, shifted
-				 * bits are replaced with logic 1. */
-				gb->gb_reg.SB = 0xFF;
+		}
 
-				/* Inform game of serial TX/RX completion. */
-				gb->gb_reg.SC &= 0x01;
-				gb->gb_reg.IF |= SERIAL_INTR;
+		/* TIMA register timing */
+		/* TODO: Change tac_enable to struct of TAC timer control bits. */
+		if(gb->hram_io[IO_TAC] & IO_TAC_ENABLE_MASK)
+		{
+			gb->counter.tima_count += inst_cycles;
+
+			while(gb->counter.tima_count >=
+				TAC_CYCLES[gb->hram_io[IO_TAC] & IO_TAC_RATE_MASK])
+			{
+				gb->counter.tima_count -=
+					TAC_CYCLES[gb->hram_io[IO_TAC] & IO_TAC_RATE_MASK];
+
+				if(++gb->hram_io[IO_TIMA] == 0)
+				{
+					gb->hram_io[IO_IF] |= TIMER_INTR;
+					/* On overflow, set TMA to TIMA. */
+					gb->hram_io[IO_TIMA] = gb->hram_io[IO_TMA];
+				}
+			}
+		}
+
+		/* TODO Check behaviour of LCD during LCD power off state. */
+		/* If LCD is off, don't update LCD state. */
+		if((gb->hram_io[IO_LCDC] & LCDC_ENABLE) == 0)
+			continue;
+
+		/* LCD Timing */
+		gb->counter.lcd_count += inst_cycles;
+
+		/* New Scanline */
+		if((gb->hram_io[IO_STAT] & STAT_MODE) & IO_STAT_MODE_VBLANK_OR_TRANSFER_MASK &&
+				gb->counter.lcd_count >= LCD_LINE_CYCLES)
+		{
+			gb->counter.lcd_count -= LCD_LINE_CYCLES;
+
+			/* LYC Update */
+			if(gb->hram_io[IO_LY] == gb->hram_io[IO_LYC])
+			{
+				gb->hram_io[IO_STAT] |= STAT_LYC_COINC;
+
+				if(gb->hram_io[IO_STAT] & STAT_LYC_INTR)
+					gb->hram_io[IO_IF] |= LCDC_INTR;
 			}
 			else
+				gb->hram_io[IO_STAT] &= 0xFB;
+
+			/* Next line */
+			gb->hram_io[IO_LY] = (gb->hram_io[IO_LY] + 1) % LCD_VERT_LINES;
+
+			/* VBLANK Start */
+			if(gb->hram_io[IO_LY] == LCD_HEIGHT)
 			{
-				/* If using external clock, and console is not
-				 * attached to any external peripheral, bits are
-				 * not shifted, so SB is not modified. */
-			}
+				gb->hram_io[IO_STAT] =
+					(gb->hram_io[IO_STAT] & ~STAT_MODE) | IO_STAT_MODE_VBLANK;
+				gb->gb_frame = 1;
+				gb->hram_io[IO_IF] |= VBLANK_INTR;
+				gb->lcd_blank = 0;
 
-			gb->counter.serial_count = 0;
-		}
-	}
-
-	/* TIMA register timing */
-	/* TODO: Change tac_enable to struct of TAC timer control bits. */
-	if(gb->gb_reg.tac_enable)
-	{
-		static const uint_fast16_t TAC_CYCLES[4] = {1024, 16, 64, 256};
-
-		gb->counter.tima_count += inst_cycles;
-
-		while(gb->counter.tima_count >= TAC_CYCLES[gb->gb_reg.tac_rate])
-		{
-			gb->counter.tima_count -= TAC_CYCLES[gb->gb_reg.tac_rate];
-
-			if(++gb->gb_reg.TIMA == 0)
-			{
-				gb->gb_reg.IF |= TIMER_INTR;
-				/* On overflow, set TMA to TIMA. */
-				gb->gb_reg.TIMA = gb->gb_reg.TMA;
-			}
-		}
-	}
-
-	/* TODO Check behaviour of LCD during LCD power off state. */
-	/* If LCD is off, don't update LCD state. */
-	if((gb->gb_reg.LCDC & LCDC_ENABLE) == 0)
-		return;
-
-	/* LCD Timing */
-	gb->counter.lcd_count += inst_cycles;
-
-	/* New Scanline */
-	if(gb->counter.lcd_count > LCD_LINE_CYCLES)
-	{
-		gb->counter.lcd_count -= LCD_LINE_CYCLES;
-
-		/* LYC Update */
-		if(gb->gb_reg.LY == gb->gb_reg.LYC)
-		{
-			gb->gb_reg.STAT |= STAT_LYC_COINC;
-
-			if(gb->gb_reg.STAT & STAT_LYC_INTR)
-				gb->gb_reg.IF |= LCDC_INTR;
-		}
-		else
-			gb->gb_reg.STAT &= 0xFB;
-
-		/* Next line */
-		gb->gb_reg.LY = (gb->gb_reg.LY + 1) % LCD_VERT_LINES;
-
-		/* VBLANK Start */
-		if(gb->gb_reg.LY == LCD_HEIGHT)
-		{
-			gb->lcd_mode = LCD_VBLANK;
-			gb->gb_frame = 1;
-			gb->gb_reg.IF |= VBLANK_INTR;
-			gb->lcd_blank = 0;
-
-			if(gb->gb_reg.STAT & STAT_MODE_1_INTR)
-				gb->gb_reg.IF |= LCDC_INTR;
+				if(gb->hram_io[IO_STAT] & STAT_MODE_1_INTR)
+					gb->hram_io[IO_IF] |= LCDC_INTR;
 
 #if ENABLE_LCD
 
-			/* If frame skip is activated, check if we need to draw
-			 * the frame or skip it. */
-			if(gb->direct.frame_skip)
-			{
-				gb->display.frame_skip_count =
-					!gb->display.frame_skip_count;
-			}
+				/* If frame skip is activated, check if we need to draw
+				 * the frame or skip it. */
+				if(gb->direct.frame_skip)
+				{
+					gb->display.frame_skip_count =
+						!gb->display.frame_skip_count;
+				}
 
-			/* If interlaced is activated, change which lines get
-			 * updated. Also, only update lines on frames that are
-			 * actually drawn when frame skip is enabled. */
-			if(gb->direct.interlace &&
+				/* If interlaced is activated, change which lines get
+				 * updated. Also, only update lines on frames that are
+				 * actually drawn when frame skip is enabled. */
+				if(gb->direct.interlace &&
 					(!gb->direct.frame_skip ||
-					 gb->display.frame_skip_count))
-			{
-				gb->display.interlace_count =
-					!gb->display.interlace_count;
-			}
-
+						gb->display.frame_skip_count))
+				{
+					gb->display.interlace_count =
+						!gb->display.interlace_count;
+				}
 #endif
+			}
+				/* Normal Line */
+			else if(gb->hram_io[IO_LY] < LCD_HEIGHT)
+			{
+				if(gb->hram_io[IO_LY] == 0)
+				{
+					/* Clear Screen */
+					gb->display.WY = gb->hram_io[IO_WY];
+					gb->display.window_clear = 0;
+				}
+
+				gb->hram_io[IO_STAT] =
+					(gb->hram_io[IO_STAT] & ~STAT_MODE) | IO_STAT_MODE_HBLANK;
+
+				if(gb->hram_io[IO_STAT] & STAT_MODE_0_INTR)
+					gb->hram_io[IO_IF] |= LCDC_INTR;
+
+				/* If halted immediately jump to next LCD mode. */
+				if(gb->counter.lcd_count < LCD_MODE_2_CYCLES)
+					inst_cycles = LCD_MODE_2_CYCLES - gb->counter.lcd_count;
+			}
 		}
-		/* Normal Line */
-		else if(gb->gb_reg.LY < LCD_HEIGHT)
+			/* OAM access */
+		else if((gb->hram_io[IO_STAT] & STAT_MODE) == IO_STAT_MODE_HBLANK &&
+			gb->counter.lcd_count >= LCD_MODE_2_CYCLES)
 		{
-			if(gb->gb_reg.LY == 0)
-			{
-				/* Clear Screen */
-				gb->display.WY = gb->gb_reg.WY;
-				gb->display.window_clear = 0;
-			}
+			gb->hram_io[IO_STAT] =
+				(gb->hram_io[IO_STAT] & ~STAT_MODE) | IO_STAT_MODE_SEARCH_OAM;
 
-			gb->lcd_mode = LCD_HBLANK;
+			if(gb->hram_io[IO_STAT] & STAT_MODE_2_INTR)
+				gb->hram_io[IO_IF] |= LCDC_INTR;
 
-			if(gb->gb_reg.STAT & STAT_MODE_0_INTR)
-				gb->gb_reg.IF |= LCDC_INTR;
+			/* If halted immediately jump to next LCD mode. */
+			if (gb->counter.lcd_count < LCD_MODE_3_CYCLES)
+				inst_cycles = LCD_MODE_3_CYCLES - gb->counter.lcd_count;
 		}
-	}
-	/* OAM access */
-	else if(gb->lcd_mode == LCD_HBLANK
-			&& gb->counter.lcd_count >= LCD_MODE_2_CYCLES)
-	{
-		gb->lcd_mode = LCD_SEARCH_OAM;
-
-		if(gb->gb_reg.STAT & STAT_MODE_2_INTR)
-			gb->gb_reg.IF |= LCDC_INTR;
-	}
-	/* Update LCD */
-	else if(gb->lcd_mode == LCD_SEARCH_OAM
-			&& gb->counter.lcd_count >= LCD_MODE_3_CYCLES)
-	{
-		gb->lcd_mode = LCD_TRANSFER;
+			/* Update LCD */
+		else if((gb->hram_io[IO_STAT] & STAT_MODE) == IO_STAT_MODE_SEARCH_OAM &&
+			gb->counter.lcd_count >= LCD_MODE_3_CYCLES)
+		{
+			gb->hram_io[IO_STAT] =
+				(gb->hram_io[IO_STAT] & ~STAT_MODE) | IO_STAT_MODE_SEARCH_TRANSFER;
 #if ENABLE_LCD
-		if(!gb->lcd_blank)
-			__gb_draw_line(gb);
+			if(!gb->lcd_blank)
+				__gb_draw_line(gb);
 #endif
-	}
+			/* If halted immediately jump to next LCD mode. */
+			if (gb->counter.lcd_count < LCD_LINE_CYCLES)
+				inst_cycles = LCD_LINE_CYCLES - gb->counter.lcd_count;
+		}
+	} while(gb->gb_halt && (gb->hram_io[IO_IF] & gb->hram_io[IO_IE]) == 0);
+	/* If halted, loop until an interrupt occurs. */
 }
 
 void gb_run_frame(struct gb_s *gb)
@@ -3562,12 +3468,6 @@ uint_fast32_t gb_get_save_size(struct gb_s *gb)
 	return ram_sizes[ram_size];
 }
 
-/**
- * Set the function used to handle serial transfer in the front-end. This is
- * optional.
- * gb_serial_transfer takes a byte to transmit and returns the received byte. If
- * no cable is connected to the console, return 0xFF.
- */
 void gb_init_serial(struct gb_s *gb,
 		    void (*gb_serial_tx)(struct gb_s*, const uint8_t),
 		    enum gb_serial_rx_ret_e (*gb_serial_rx)(struct gb_s*,
@@ -3597,8 +3497,9 @@ void gb_reset(struct gb_s *gb)
 {
 	gb->gb_halt = 0;
 	gb->gb_ime = 1;
+#if PEANUT_GB_USE_BIOS
 	gb->gb_bios_enable = 0;
-	gb->lcd_mode = LCD_HBLANK;
+#endif
 
 	/* Initialise MBC values. */
 	gb->selected_rom_bank = 1;
@@ -3607,54 +3508,53 @@ void gb_reset(struct gb_s *gb)
 	gb->cart_mode_select = 0;
 
 	/* Initialise CPU registers as though a DMG. */
-	gb->cpu_reg.af = 0x01B0;
-	gb->cpu_reg.bc = 0x0013;
-	gb->cpu_reg.de = 0x00D8;
-	gb->cpu_reg.hl = 0x014D;
-	gb->cpu_reg.sp = 0xFFFE;
+	gb->cpu_reg.a = 0x01;
+	gb->cpu_reg.f_bits.z = 1;
+	gb->cpu_reg.f_bits.n = 0;
+	gb->cpu_reg.f_bits.h = 1;
+	gb->cpu_reg.f_bits.c = 1;
+	gb->cpu_reg.bc.reg = 0x0013;
+	gb->cpu_reg.de.reg = 0x00D8;
+	gb->cpu_reg.hl.reg = 0x014D;
+	gb->cpu_reg.sp.reg = 0xFFFE;
 	/* TODO: Add BIOS support. */
-	gb->cpu_reg.pc = 0x0100;
+	gb->cpu_reg.pc.reg = 0x0100;
 
 	gb->counter.lcd_count = 0;
 	gb->counter.div_count = 0;
 	gb->counter.tima_count = 0;
 	gb->counter.serial_count = 0;
 
-	gb->gb_reg.TIMA      = 0x00;
-	gb->gb_reg.TMA       = 0x00;
-	gb->gb_reg.TAC       = 0xF8;
-	gb->gb_reg.DIV       = 0xAC;
+	memset(gb->hram_io, 0xFF, HRAM_IO_SIZE);
 
-	gb->gb_reg.IF        = 0xE1;
-
-	gb->gb_reg.LCDC      = 0x91;
-	gb->gb_reg.SCY       = 0x00;
-	gb->gb_reg.SCX       = 0x00;
-	gb->gb_reg.LYC       = 0x00;
+	gb->hram_io[IO_TIMA] = 0x00;
+	gb->hram_io[IO_TMA ] = 0x00;
+	gb->hram_io[IO_TAC ] = 0xF8;
+	gb->hram_io[IO_DIV ] = 0xAC;
+	gb->hram_io[IO_IF  ] = 0xE1;
+	gb->hram_io[IO_LCDC] = 0x91;
+	gb->hram_io[IO_STAT] = STAT_MODE & IO_STAT_MODE_HBLANK;
+	gb->hram_io[IO_SCY ] = 0x00;
+	gb->hram_io[IO_SCX ] = 0x00;
+	gb->hram_io[IO_LYC ] = 0x00;
 
 	/* Appease valgrind for invalid reads and unconditional jumps. */
-	gb->gb_reg.SC = 0x7E;
-	gb->gb_reg.STAT = 0;
-	gb->gb_reg.LY = 0;
+	gb->hram_io[IO_SC] = 0x7E;
+	gb->hram_io[IO_LY] = 0;
 
 	__gb_write(gb, 0xFF47, 0xFC);    // BGP
 	__gb_write(gb, 0xFF48, 0xFF);    // OBJP0
 	__gb_write(gb, 0xFF49, 0x0F);    // OBJP1
-	gb->gb_reg.WY        = 0x00;
-	gb->gb_reg.WX        = 0x00;
-	gb->gb_reg.IE        = 0x00;
+	gb->hram_io[IO_WY] = 0x00;
+	gb->hram_io[IO_WX] = 0x00;
+	gb->hram_io[IO_IE] = 0x00;
 
 	gb->direct.joypad = 0xFF;
-	gb->direct.ended = 0;
-	gb->gb_reg.P1 = 0xCF;
+	gb->hram_io[IO_JOYP] = 0xCF;
 
 	memset(gb->vram, 0x00, VRAM_SIZE);
 }
 
-/**
- * Initialise the emulator context. gb_reset() is also called to initialise
- * the CPU.
- */
 enum gb_init_error_e gb_init(struct gb_s *gb,
 			     uint8_t (*gb_rom_read)(struct gb_s*, const uint_fast32_t),
 			     uint8_t (*gb_cart_ram_read)(struct gb_s*, const uint_fast32_t),
@@ -3675,7 +3575,7 @@ enum gb_init_error_e gb_init(struct gb_s *gb,
 	 * TODO: HuC3 is unsupported.
 	 * TODO: HuC1 is unsupported.
 	 **/
-	const uint8_t cart_mbc[] =
+	const int8_t cart_mbc[] =
 	{
 		0, 1, 1, 1, -1, 2, 2, -1, 0, 0, -1, 0, 0, 0, -1, 3,
 		3, 3, 3, 3, -1, -1, -1, -1, -1, 5, 5, 5, 5, 5, 5, -1
@@ -3719,7 +3619,7 @@ enum gb_init_error_e gb_init(struct gb_s *gb,
 		const uint8_t mbc_value = gb->gb_rom_read(gb, mbc_location);
 
 		if(mbc_value > sizeof(cart_mbc) - 1 ||
-				(gb->mbc = cart_mbc[mbc_value]) == 255u)
+				(gb->mbc = cart_mbc[mbc_value]) == -1)
 			return GB_INIT_CARTRIDGE_UNSUPPORTED;
 	}
 
@@ -3735,13 +3635,6 @@ enum gb_init_error_e gb_init(struct gb_s *gb,
 	return GB_INIT_NO_ERROR;
 }
 
-/**
- * Returns the title of ROM.
- *
- * \param gb		Initialised context.
- * \param title_str	Allocated string at least 16 characters.
- * \returns		Pointer to start of string, null terminated.
- */
 const char* gb_get_rom_name(struct gb_s* gb, char *title_str)
 {
 	uint_fast16_t title_loc = 0x134;
@@ -3785,3 +3678,193 @@ void gb_init_lcd(struct gb_s *gb,
 	return;
 }
 #endif
+
+/**
+ * This was taken from SameBoy, which is released under MIT Licence.
+ */
+void gb_tick_rtc(struct gb_s *gb)
+{
+	/* is timer running? */
+	if((gb->cart_rtc[4] & 0x40) == 0)
+	{
+		if(++gb->rtc_bits.sec == 60)
+		{
+			gb->rtc_bits.sec = 0;
+
+			if(++gb->rtc_bits.min == 60)
+			{
+				gb->rtc_bits.min = 0;
+
+				if(++gb->rtc_bits.hour == 24)
+				{
+					gb->rtc_bits.hour = 0;
+
+					if(++gb->rtc_bits.yday == 0)
+					{
+						if(gb->rtc_bits.high & 1)  /* Bit 8 of days*/
+						{
+							gb->rtc_bits.high |= 0x80; /* Overflow bit */
+						}
+
+						gb->rtc_bits.high ^= 1;
+					}
+				}
+			}
+		}
+	}
+}
+
+void gb_set_rtc(struct gb_s *gb, const struct tm * const time)
+{
+	gb->cart_rtc[0] = time->tm_sec;
+	gb->cart_rtc[1] = time->tm_min;
+	gb->cart_rtc[2] = time->tm_hour;
+	gb->cart_rtc[3] = time->tm_yday & 0xFF; /* Low 8 bits of day counter. */
+	gb->cart_rtc[4] = time->tm_yday >> 8; /* High 1 bit of day counter. */
+}
+
+/** Function prototypes: Required functions **/
+/**
+ * Initialises the emulator context to a known state. Call this before calling
+ * any other peanut-gb function.
+ * To reset the emulator, you can call gb_reset() instead.
+ *
+ * \param gb	Allocated emulator context. Must not be NULL.
+ * \param gb_rom_read Pointer to function that reads ROM data. ROM banking is
+ * 		already handled by Peanut-GB. Must not be NULL.
+ * \param gb_cart_ram_read Pointer to function that reads Cart RAM. Must not be
+ * 		NULL.
+ * \param gb_cart_ram_write Pointer to function to writes to Cart RAM. Must not
+ * 		be NULL.
+ * \param gb_error Pointer to function that is called when an unrecoverable
+ *		error occurs. Must not be NULL. Returning from this
+ *		function is undefined and will result in SIGABRT.
+ * \param priv	Private data that is stored within the emulator context. Set to
+ * 		NULL if unused.
+ * \returns	0 on success or an enum that describes the error.
+ */
+enum gb_init_error_e gb_init(struct gb_s *gb,
+			     uint8_t (*gb_rom_read)(struct gb_s*, const uint_fast32_t),
+			     uint8_t (*gb_cart_ram_read)(struct gb_s*, const uint_fast32_t),
+			     void (*gb_cart_ram_write)(struct gb_s*, const uint_fast32_t, const uint8_t),
+			     void (*gb_error)(struct gb_s*, const enum gb_error_e, const uint16_t),
+			     void *priv);
+
+/**
+ * Executes the emulator and runs for one frame.
+ *
+ * \param	An initialised emulator context. Must not be NULL.
+ */
+void gb_run_frame(struct gb_s *gb);
+
+/** Function prototypes: Optional Functions **/
+/**
+ * Reset the emulator, like turning the Game Boy off and on again.
+ * This function can be called at any time.
+ *
+ * \param	An initialised emulator context. Must not be NULL.
+ */
+void gb_reset(struct gb_s *gb);
+
+/**
+ * Initialises the display context of the emulator. Only available when
+ * ENABLE_LCD is defined to a non-zero value.
+ * The pixel data sent to lcd_draw_line comes with both shade and layer data.
+ * The first two least significant bits are the shade data (black, dark, light,
+ * white). Bits 4 and 5 are layer data (OBJ0, OBJ1, BG), which can be used to
+ * add more colours to the game in the same way that the Game Boy Color does to
+ * older Game Boy games.
+ * This function can be called at any time.
+ *
+ * \param gb	An initialised emulator context. Must not be NULL.
+ * \param lcd_draw_line Pointer to function that draws the 2-bit pixel data on the line
+ *		"line". Must not be NULL.
+ */
+#if ENABLE_LCD
+void gb_init_lcd(struct gb_s *gb,
+		void (*lcd_draw_line)(struct gb_s *gb,
+			const uint8_t *pixels,
+			const uint_fast8_t line));
+#endif
+
+/**
+ * Initialises the serial connection of the emulator. This function is optional,
+ * and if not called, the emulator will assume that no link cable is connected
+ * to the game.
+ *
+ * \param gb	An initialised emulator context. Must not be NULL.
+ * \param gb_serial_tx Pointer to function that transmits a byte of data over
+ *		the serial connection. Must not be NULL.
+ * \param gb_serial_rx Pointer to function that receives a byte of data over the
+ *		serial connection. If no byte is recieved,
+ *		return GB_SERIAL_RX_NO_CONNECTION. Must not be NULL.
+ */
+void gb_init_serial(struct gb_s *gb,
+		    void (*gb_serial_tx)(struct gb_s*, const uint8_t),
+		    enum gb_serial_rx_ret_e (*gb_serial_rx)(struct gb_s*,
+			    uint8_t*));
+
+/**
+ * Obtains the save size of the game (size of the Cart RAM). Required by the
+ * frontend to allocate enough memory for the Cart RAM.
+ *
+ * \param gb	An initialised emulator context. Must not be NULL.
+ * \returns	Size of the Cart RAM in bytes. 0 if Cartridge has not battery
+ *		backed RAM.
+ */
+uint_fast32_t gb_get_save_size(struct gb_s *gb);
+
+/**
+ * Calculates and returns a hash of the game header in the same way the Game
+ * Boy Color does for colourising old Game Boy games. The frontend can use this
+ * hash to automatically set a colour palette.
+ *
+ * \param gb	An initialised emulator context. Must not be NULL.
+ * \returns	Hash of the game header.
+ */
+uint8_t gb_colour_hash(struct gb_s *gb);
+
+/**
+ * Returns the title of ROM.
+ *
+ * \param gb	An initialised emulator context. Must not be NULL.
+ * \param title_str Allocated string at least 16 characters.
+ * \returns	Pointer to start of string, null terminated.
+ */
+const char* gb_get_rom_name(struct gb_s* gb, char *title_str);
+
+/**
+ * Tick the internal RTC by one second. This does not affect games with no RTC
+ * support.
+ *
+ * \param gb	An initialised emulator context. Must not be NULL.
+ */
+void gb_tick_rtc(struct gb_s *gb);
+
+/**
+ * Set initial values in RTC.
+ * Should be called after gb_init().
+ *
+ * \param gb	An initialised emulator context. Must not be NULL.
+ * \param time	Time structure with date and time.
+ */
+void gb_set_rtc(struct gb_s *gb, const struct tm * const time);
+
+/* Undefine CPU Flag helper functions. */
+#undef PEANUT_GB_CPUFLAG_MASK_CARRY
+#undef PEANUT_GB_CPUFLAG_MASK_HALFC
+#undef PEANUT_GB_CPUFLAG_MASK_ARITH
+#undef PEANUT_GB_CPUFLAG_MASK_ZERO
+#undef PEANUT_GB_CPUFLAG_BIT_CARRY
+#undef PEANUT_GB_CPUFLAG_BIT_HALFC
+#undef PEANUT_GB_CPUFLAG_BIT_ARITH
+#undef PEANUT_GB_CPUFLAG_BIT_ZERO
+#undef PGB_SET_CARRY
+#undef PGB_SET_HALFC
+#undef PGB_SET_ARITH
+#undef PGB_SET_ZERO
+#undef PGB_GET_CARRY
+#undef PGB_GET_HALFC
+#undef PGB_GET_ARITH
+#undef PGB_GET_ZERO
+#endif //PEANUT_GB_H