Remove the SNES Open Bus behaviour by default. Also simplify translation again.

SNES Open Bus is a quirk of the memory subsystem that allow reads of invalid addresses to return the last byte read from memory. However, it is seldom needed by a game, and it costs 1 to 3 MIPS instructions per SNES instruction to emulate.

If you need SNES Open Bus, you can remove -DNO_OPEN_BUS from the Makefile.

10 files changed, 343 insertions, 64 deletions

diff --git a/source/cpuaddr.h b/source/cpuaddr.h
index 76344db..4f5febf 100644
--- a/source/cpuaddr.h
+++ b/source/cpuaddr.h
@@ -146,10 +146,14 @@ void AbsoluteIndexedIndirect (AccessMode a)
 #ifndef SA1_OPCODES
     CPU.Cycles += CPU.MemSpeedx2;
 #endif
+#ifndef NO_OPEN_BUS
     OpenBus = *(CPU.PC + 1);
+#endif
     CPU.PC += 2;
     OpAddress = S9xGetWord (ICPU.ShiftedPB + OpAddress);
+#ifndef NO_OPEN_BUS
     if(a&READ) OpenBus = (uint8)(OpAddress>>8);
+#endif
 }
 
 void AbsoluteIndirectLong (AccessMode a)
@@ -163,13 +167,19 @@ void AbsoluteIndirectLong (AccessMode a)
 #ifndef SA1_OPCODES
     CPU.Cycles += CPU.MemSpeedx2;
 #endif
+#ifndef NO_OPEN_BUS
     OpenBus = *(CPU.PC + 1);
+#endif
     CPU.PC += 2;
+#ifndef NO_OPEN_BUS
     if(a&READ) {
 	OpAddress = S9xGetWord (OpAddress) | ((OpenBus=S9xGetByte (OpAddress + 2)) << 16);
     } else {
+#endif
     OpAddress = S9xGetWord (OpAddress) | (S9xGetByte (OpAddress + 2) << 16);
+#ifndef NO_OPEN_BUS
     }
+#endif
 }
 
 void AbsoluteIndirect (AccessMode a)
@@ -183,10 +193,14 @@ void AbsoluteIndirect (AccessMode a)
 #ifndef SA1_OPCODES
     CPU.Cycles += CPU.MemSpeedx2;
 #endif
+#ifndef NO_OPEN_BUS
     OpenBus = *(CPU.PC + 1);
+#endif
     CPU.PC += 2;
     OpAddress = S9xGetWord (OpAddress);
+#ifndef NO_OPEN_BUS
     if(a&READ) OpenBus = (uint8)(OpAddress>>8);
+#endif
     OpAddress += ICPU.ShiftedPB;
 }
 
@@ -197,7 +211,9 @@ void Absolute (AccessMode a)
 #else
     OpAddress = *CPU.PC + (*(CPU.PC + 1) << 8) + ICPU.ShiftedDB;
 #endif
+#ifndef NO_OPEN_BUS
     if(a&READ) OpenBus = *(CPU.PC+1);
+#endif
     CPU.PC += 2;
 #ifndef SA1_OPCODES
     CPU.Cycles += CPU.MemSpeedx2;
@@ -211,7 +227,9 @@ void AbsoluteLong (AccessMode a)
 #else
     OpAddress = *CPU.PC + (*(CPU.PC + 1) << 8) + (*(CPU.PC + 2) << 16);
 #endif
+#ifndef NO_OPEN_BUS
     if(a&READ) OpenBus = *(CPU.PC+2);
+#endif
     CPU.PC += 3;
 #ifndef SA1_OPCODES
     CPU.Cycles += CPU.MemSpeedx2 + CPU.MemSpeed;
@@ -220,7 +238,9 @@ void AbsoluteLong (AccessMode a)
 
 void Direct(AccessMode a)
 {
+#ifndef NO_OPEN_BUS
     if(a&READ) OpenBus = *CPU.PC;
+#endif
     OpAddress = (*CPU.PC++ + Registers.D.W) & 0xffff;
 #ifndef SA1_OPCODES
     CPU.Cycles += CPU.MemSpeed;
@@ -230,14 +250,18 @@ void Direct(AccessMode a)
 
 void DirectIndirectIndexed (AccessMode a)
 {
+#ifndef NO_OPEN_BUS
     OpenBus = *CPU.PC;
+#endif
     OpAddress = (*CPU.PC++ + Registers.D.W) & 0xffff;
 #ifndef SA1_OPCODES
     CPU.Cycles += CPU.MemSpeed;
 #endif
 
     OpAddress = S9xGetWord (OpAddress);
+#ifndef NO_OPEN_BUS
     if(a&READ) OpenBus = (uint8)(OpAddress>>8);
+#endif
     OpAddress += ICPU.ShiftedDB + Registers.Y.W;
 
 //    if (Registers.DL != 0) CPU.Cycles += ONE_CYCLE;
@@ -247,30 +271,40 @@ void DirectIndirectIndexed (AccessMode a)
 
 void DirectIndirectIndexedLong (AccessMode a)
 {
+#ifndef NO_OPEN_BUS
     OpenBus = *CPU.PC;
+#endif
     OpAddress = (*CPU.PC++ + Registers.D.W) & 0xffff;
 #ifndef SA1_OPCODES
     CPU.Cycles += CPU.MemSpeed;
 #endif
 
+#ifndef NO_OPEN_BUS
     if(a&READ){
 	OpAddress = S9xGetWord (OpAddress) + ((OpenBus = S9xGetByte (OpAddress + 2)) << 16) + Registers.Y.W;
     } else {
+#endif
 	OpAddress = S9xGetWord (OpAddress) + (S9xGetByte (OpAddress + 2) << 16) + Registers.Y.W;
+#ifndef NO_OPEN_BUS
     }
+#endif
 //    if (Registers.DL != 0) CPU.Cycles += ONE_CYCLE;
 }
 
 void DirectIndexedIndirect(AccessMode a)
 {
+#ifndef NO_OPEN_BUS
     OpenBus = *CPU.PC;
+#endif
     OpAddress = (*CPU.PC++ + Registers.D.W + Registers.X.W) & 0xffff;
 #ifndef SA1_OPCODES
     CPU.Cycles += CPU.MemSpeed;
 #endif
 
     OpAddress = S9xGetWord (OpAddress);
+#ifndef NO_OPEN_BUS
     if(a&READ) OpenBus = (uint8)(OpAddress>>8);
+#endif
     OpAddress += ICPU.ShiftedDB;
 
 #ifndef SA1_OPCODES
@@ -283,36 +317,34 @@ void DirectIndexedIndirect(AccessMode a)
 
 void DirectIndexedX (AccessMode a)
 {
+#ifndef NO_OPEN_BUS
 	if(a&READ) OpenBus = *CPU.PC;
+#endif
     OpAddress = (*CPU.PC++ + Registers.D.W + Registers.X.W);
     OpAddress &= CheckEmulation() ? 0xff : 0xffff;
 
 #ifndef SA1_OPCODES
-    CPU.Cycles += CPU.MemSpeed;
-#endif
-
-#ifndef SA1_OPCODES
+    CPU.Cycles += CPU.MemSpeed + ONE_CYCLE;
 //    if (Registers.DL != 0)
 //	CPU.Cycles += TWO_CYCLES;
 //    else
-	CPU.Cycles += ONE_CYCLE;
+//	CPU.Cycles += ONE_CYCLE;
 #endif
 }
 
 void DirectIndexedY (AccessMode a)
 {
+#ifndef NO_OPEN_BUS
 	if(a&READ) OpenBus = *CPU.PC;
+#endif
     OpAddress = (*CPU.PC++ + Registers.D.W + Registers.Y.W);
     OpAddress &= CheckEmulation() ? 0xff : 0xffff;
 #ifndef SA1_OPCODES
-    CPU.Cycles += CPU.MemSpeed;
-#endif
-
-#ifndef SA1_OPCODES
+    CPU.Cycles += CPU.MemSpeed + ONE_CYCLE;
 //    if (Registers.DL != 0)
 //	CPU.Cycles += TWO_CYCLES;
 //    else
-	CPU.Cycles += ONE_CYCLE;
+//	CPU.Cycles += ONE_CYCLE;
 #endif
 }
 
@@ -324,7 +356,9 @@ void AbsoluteIndexedX (AccessMode a)
     OpAddress = ICPU.ShiftedDB + *CPU.PC + (*(CPU.PC + 1) << 8) +
 		Registers.X.W;
 #endif
+#ifndef NO_OPEN_BUS
     if(a&READ) OpenBus = *(CPU.PC+1);
+#endif
     CPU.PC += 2;
 #ifndef SA1_OPCODES
     CPU.Cycles += CPU.MemSpeedx2;
@@ -341,7 +375,9 @@ void AbsoluteIndexedY (AccessMode a)
     OpAddress = ICPU.ShiftedDB + *CPU.PC + (*(CPU.PC + 1) << 8) +
 		Registers.Y.W;
 #endif    
+#ifndef NO_OPEN_BUS
     if(a&READ) OpenBus = *(CPU.PC+1);
+#endif
     CPU.PC += 2;
 #ifndef SA1_OPCODES
     CPU.Cycles += CPU.MemSpeedx2;
@@ -357,7 +393,9 @@ void AbsoluteLongIndexedX (AccessMode a)
 #else
     OpAddress = (*CPU.PC + (*(CPU.PC + 1) << 8) + (*(CPU.PC + 2) << 16) + Registers.X.W) & 0xffffff;
 #endif
+#ifndef NO_OPEN_BUS
     if(a&READ) OpenBus = *(CPU.PC+2);
+#endif
     CPU.PC += 3;
 #ifndef SA1_OPCODES
     CPU.Cycles += CPU.MemSpeedx2 + CPU.MemSpeed;
@@ -366,13 +404,17 @@ void AbsoluteLongIndexedX (AccessMode a)
 
 void DirectIndirect (AccessMode a)
 {
+#ifndef NO_OPEN_BUS
     OpenBus = *CPU.PC;
+#endif
     OpAddress = (*CPU.PC++ + Registers.D.W) & 0xffff;
 #ifndef SA1_OPCODES
     CPU.Cycles += CPU.MemSpeed;
 #endif
     OpAddress = S9xGetWord (OpAddress);
+#ifndef NO_OPEN_BUS
     if(a&READ) OpenBus = (uint8)(OpAddress>>8);
+#endif
     OpAddress += ICPU.ShiftedDB;
 
 //    if (Registers.DL != 0) CPU.Cycles += ONE_CYCLE;
@@ -380,39 +422,49 @@ void DirectIndirect (AccessMode a)
 
 void DirectIndirectLong (AccessMode a)
 {
+#ifndef NO_OPEN_BUS
     OpenBus = *CPU.PC;
+#endif
     OpAddress = (*CPU.PC++ + Registers.D.W) & 0xffff;
 #ifndef SA1_OPCODES
     CPU.Cycles += CPU.MemSpeed;
 #endif
+#ifndef NO_OPEN_BUS
     if(a&READ){
 	OpAddress = S9xGetWord (OpAddress) + ((OpenBus=S9xGetByte (OpAddress + 2)) << 16);
     } else {
+#endif
 	OpAddress = S9xGetWord (OpAddress) + (S9xGetByte (OpAddress + 2) << 16);
+#ifndef NO_OPEN_BUS
     }
+#endif
 //    if (Registers.DL != 0) CPU.Cycles += ONE_CYCLE;
 }
 
 void StackRelative (AccessMode a)
 {
+#ifndef NO_OPEN_BUS
     if(a&READ) OpenBus = *CPU.PC;
+#endif
     OpAddress = (*CPU.PC++ + Registers.S.W) & 0xffff;
 #ifndef SA1_OPCODES
-    CPU.Cycles += CPU.MemSpeed;
-    CPU.Cycles += ONE_CYCLE;
+    CPU.Cycles += CPU.MemSpeed + ONE_CYCLE;
 #endif
 }
 
 void StackRelativeIndirectIndexed (AccessMode a)
 {
+#ifndef NO_OPEN_BUS
     OpenBus = *CPU.PC;
+#endif
     OpAddress = (*CPU.PC++ + Registers.S.W) & 0xffff;
 #ifndef SA1_OPCODES
-    CPU.Cycles += CPU.MemSpeed;
-    CPU.Cycles += TWO_CYCLES;
+    CPU.Cycles += CPU.MemSpeed + TWO_CYCLES;
 #endif
     OpAddress = S9xGetWord (OpAddress);
+#ifndef NO_OPEN_BUS
     if(a&READ) OpenBus = (uint8)(OpAddress>>8);
+#endif
     OpAddress = (OpAddress + ICPU.ShiftedDB +
 		 Registers.Y.W) & 0xffffff;
 }
diff --git a/source/cpuops.cpp b/source/cpuops.cpp
index c5adc67..967ca9f 100644
--- a/source/cpuops.cpp
+++ b/source/cpuops.cpp
@@ -3556,7 +3556,9 @@ static void Op00 (void)
 	PushW (CPU.PC - CPU.PCBase + 1);
 	S9xPackStatus ();
 	PushB (Registers.PL);
+#ifndef NO_OPEN_BUS
 	OpenBus = Registers.PL;
+#endif
 	ClearDecimal ();
 	SetIRQ ();
 
@@ -3572,7 +3574,9 @@ static void Op00 (void)
 	PushW (CPU.PC - CPU.PCBase);
 	S9xPackStatus ();
 	PushB (Registers.PL);
+#ifndef NO_OPEN_BUS
 	OpenBus = Registers.PL;
+#endif
 	ClearDecimal ();
 	SetIRQ ();
 
@@ -3607,7 +3611,9 @@ void S9xOpcode_IRQ (void)
 	PushW (CPU.PC - CPU.PCBase);
 	S9xPackStatus ();
 	PushB (Registers.PL);
+#ifndef NO_OPEN_BUS
 	OpenBus = Registers.PL;
+#endif
 	ClearDecimal ();
 	SetIRQ ();
 
@@ -3632,7 +3638,9 @@ void S9xOpcode_IRQ (void)
 	PushW (CPU.PC - CPU.PCBase);
 	S9xPackStatus ();
 	PushB (Registers.PL);
+#ifndef NO_OPEN_BUS
 	OpenBus = Registers.PL;
+#endif
 	ClearDecimal ();
 	SetIRQ ();
 
@@ -3669,7 +3677,9 @@ void S9xOpcode_NMI (void)
 	PushW (CPU.PC - CPU.PCBase);
 	S9xPackStatus ();
 	PushB (Registers.PL);
+#ifndef NO_OPEN_BUS
 	OpenBus = Registers.PL;
+#endif
 	ClearDecimal ();
 	SetIRQ ();
 
@@ -3694,7 +3704,9 @@ void S9xOpcode_NMI (void)
 	PushW (CPU.PC - CPU.PCBase);
 	S9xPackStatus ();
 	PushB (Registers.PL);
+#ifndef NO_OPEN_BUS
 	OpenBus = Registers.PL;
+#endif
 	ClearDecimal ();
 	SetIRQ ();
 
@@ -3730,7 +3742,9 @@ static void Op02 (void)
 	PushW (CPU.PC - CPU.PCBase + 1);
 	S9xPackStatus ();
 	PushB (Registers.PL);
+#ifndef NO_OPEN_BUS
 	OpenBus = Registers.PL;
+#endif
 	ClearDecimal ();
 	SetIRQ ();
 
@@ -3746,7 +3760,9 @@ static void Op02 (void)
 	PushW (CPU.PC - CPU.PCBase);
 	S9xPackStatus ();
 	PushB (Registers.PL);
+#ifndef NO_OPEN_BUS
 	OpenBus = Registers.PL;
+#endif
 	ClearDecimal ();
 	SetIRQ ();
 
@@ -3905,7 +3921,10 @@ static void Op54X1 (void)
     
     Registers.DB = *CPU.PC++;
     ICPU.ShiftedDB = Registers.DB << 16;
-    OpenBus = SrcBank = *CPU.PC++;
+#ifndef NO_OPEN_BUS
+    OpenBus =
+#endif
+		SrcBank = *CPU.PC++;
 
     S9xSetByte (S9xGetByte ((SrcBank << 16) + Registers.X.W), 
 	     ICPU.ShiftedDB + Registers.Y.W);
@@ -3927,7 +3946,10 @@ static void Op54X0 (void)
     
     Registers.DB = *CPU.PC++;
     ICPU.ShiftedDB = Registers.DB << 16;
-    OpenBus = SrcBank = *CPU.PC++;
+#ifndef NO_OPEN_BUS
+    OpenBus =
+#endif
+		SrcBank = *CPU.PC++;
 
     S9xSetByte (S9xGetByte ((SrcBank << 16) + Registers.X.W), 
 	     ICPU.ShiftedDB + Registers.Y.W);
@@ -3948,7 +3970,10 @@ static void Op44X1 (void)
 #endif    
     Registers.DB = *CPU.PC++;
     ICPU.ShiftedDB = Registers.DB << 16;
-    OpenBus = SrcBank = *CPU.PC++;
+#ifndef NO_OPEN_BUS
+    OpenBus =
+#endif
+		SrcBank = *CPU.PC++;
     S9xSetByte (S9xGetByte ((SrcBank << 16) + Registers.X.W), 
 	     ICPU.ShiftedDB + Registers.Y.W);
 
@@ -3968,7 +3993,10 @@ static void Op44X0 (void)
 #endif    
     Registers.DB = *CPU.PC++;
     ICPU.ShiftedDB = Registers.DB << 16;
-    OpenBus = SrcBank = *CPU.PC++;
+#ifndef NO_OPEN_BUS
+    OpenBus =
+#endif
+		SrcBank = *CPU.PC++;
     S9xSetByte (S9xGetByte ((SrcBank << 16) + Registers.X.W), 
 	     ICPU.ShiftedDB + Registers.Y.W);
 
diff --git a/source/getset.h b/source/getset.h
index f04bf95..9b94b22 100644
--- a/source/getset.h
+++ b/source/getset.h
@@ -98,10 +98,12 @@
 #include "obc1.h"
 #include "seta.h"
 
+#ifndef NO_OPEN_BUS
 extern "C"
 {
 	extern uint8 OpenBus;
 }
+#endif
 
 uint8 S9xGetByte (uint32 Address)
 {
@@ -178,8 +180,11 @@ uint8 S9xGetByte (uint32 Address)
  #ifdef DEBUGGER
  		printf ("DEBUG R(B) %06x\n", Address);
  #endif
- 		return OpenBus;
- 
+#ifndef NO_OPEN_BUS
+		return OpenBus;
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
 
 
 	default:
@@ -193,7 +198,11 @@ uint8 S9xGetByte (uint32 Address)
 #ifdef DEBUGGER
 		printf ("R(B) %06x\n", Address);
 #endif
+#ifndef NO_OPEN_BUS
 		return OpenBus;
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
     }
 }
 
@@ -201,8 +210,13 @@ uint16 S9xGetWord (uint32 Address)
 {
     if ((Address & 0x0fff) == 0x0fff)
     {
-		OpenBus=S9xGetByte (Address);
+#ifndef NO_OPEN_BUS
+		OpenBus = S9xGetByte (Address);
 		return (OpenBus | (S9xGetByte (Address + 1) << 8));
+#else
+		uint8 Split = S9xGetByte (Address);
+		return (Split | (S9xGetByte (Address + 1) << 8));
+#endif
     }
     int block;
     uint8 *GetAddress = Memory.Map [block = (Address >> MEMMAP_SHIFT) & MEMMAP_MASK];
@@ -302,8 +316,11 @@ uint16 S9xGetWord (uint32 Address)
  #ifdef DEBUGGER
  		printf ("DEBUG R(W) %06x\n", Address);
  #endif
- 		return (OpenBus | (OpenBus<<8));
-
+#ifndef NO_OPEN_BUS
+		return (OpenBus | (OpenBus<<8));
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
 
     default:
     case CMemory::MAP_NONE:
@@ -316,7 +333,11 @@ uint16 S9xGetWord (uint32 Address)
 #ifdef DEBUGGER
 		printf ("R(W) %06x\n", Address);
 #endif
+#ifndef NO_OPEN_BUS
 		return (OpenBus | (OpenBus<<8));
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
     }
 }
 
diff --git a/source/globals.cpp b/source/globals.cpp
index 0103f7e..f00a621 100644
--- a/source/globals.cpp
+++ b/source/globals.cpp
@@ -157,7 +157,9 @@ uint32 Work32 = 0;
 signed char Int8 = 0;
 short Int16 = 0;
 long Int32 = 0;
-unsigned char OpenBus = 0;
+#ifndef NO_OPEN_BUS
+uint8 OpenBus = 0;
+#endif
 
 
 END_EXTERN_C
diff --git a/source/memmap.h b/source/memmap.h
index 58f0c9f..f838065 100644
--- a/source/memmap.h
+++ b/source/memmap.h
@@ -276,7 +276,7 @@ bool8 LoadZip(const char* zipname,
 END_EXTERN_C
 
 extern "C" {
-void S9xAutoSaveSRAM ();
+	void S9xAutoSaveSRAM ();
 }
 
 #ifdef NO_INLINE_SET_GET
@@ -288,9 +288,12 @@ void S9xSetPCBase (uint32 Address);
 uint8 *S9xGetMemPointer (uint32 Address);
 uint8 *GetBasePointer (uint32 Address);
 
-extern "C"{
-extern uint8 OpenBus;
+#ifndef NO_OPEN_BUS
+extern "C" {
+	extern uint8 OpenBus;
 }
+#endif
+
 #else
 #define INLINE inline
 #include "getset.h"
diff --git a/source/nds/gui.c b/source/nds/gui.c
index 3201665..61a3b58 100644
--- a/source/nds/gui.c
+++ b/source/nds/gui.c
@@ -40,6 +40,8 @@ char	rom_path[MAX_PATH];
 char	gamepak_name[MAX_PATH];
 char	gcheat_filename[MAX_PATH];
 
+// If adding a language, make sure you update the size of the array in
+// message.h too.
 char *lang[3] =
 	{ 
 		"English",					// 0
@@ -2966,8 +2968,6 @@ u32 menu(u16 *screen)
 
     char *enable_disable_options[] = { (char*)&msg[MSG_EN_DIS_ABLE_0], (char*)&msg[MSG_EN_DIS_ABLE_1] };
 
-    char *language_options[] = { (char*) &lang[0], (char*) &lang[1], (char*) &lang[2] };
-
     char *keyremap_options[] = {(char*)&msg[MSG_KEY_MAP_NONE], (char*)&msg[MSG_KEY_MAP_A], (char*)&msg[MSG_KEY_MAP_B], 
                                 (char*)&msg[MSG_KEY_MAP_SL], (char*)&msg[MSG_KEY_MAP_ST], (char*)&msg[MSG_KEY_MAP_RT], 
                                 (char*)&msg[MSG_KEY_MAP_LF], (char*)&msg[MSG_KEY_MAP_UP], (char*)&msg[MSG_KEY_MAP_DW], 
@@ -3124,8 +3124,8 @@ u32 menu(u16 *screen)
 	//CPU speed
 	/* 01 */ NUMERIC_SELECTION_OPTION(NULL, &msg[MSG_SUB_MENU_42], &clock_speed_number, 6, NULL, 1),
 
-	/* 02 */ STRING_SELECTION_OPTION(language_set, NULL, &msg[MSG_SUB_MENU_41], language_options, 
-        &emu_config.language, sizeof(language_options) / sizeof(language_options[0]) /* number of possible languages */, NULL, ACTION_TYPE, 2),
+	/* 02 */ STRING_SELECTION_OPTION(language_set, NULL, &msg[MSG_SUB_MENU_41], lang, 
+        &emu_config.language, sizeof(lang) / sizeof(lang[0]) /* number of possible languages */, NULL, ACTION_TYPE, 2),
 
 	/* 03 */ STRING_SELECTION_OPTION(NULL, show_card_space, &msg[MSG_SUB_MENU_43], NULL, 
         &desert, 2, NULL, PASSIVE_TYPE | HIDEN_TYPE, 3),
diff --git a/source/nds/message.h b/source/nds/message.h
index 9292d3f..4a0acd2 100644
--- a/source/nds/message.h
+++ b/source/nds/message.h
@@ -168,6 +168,8 @@ enum LANGUAGE{
 	FRENCH
 };
 
+extern char* lang[3]; // Allocated in gui.c, needs to match the languages ^
+
 char *msg[MSG_END+1];
 char msg_data[16 * 1024];
 
diff --git a/source/ppu.cpp b/source/ppu.cpp
index 389bdd2..8ba7a5f 100644
--- a/source/ppu.cpp
+++ b/source/ppu.cpp
@@ -1071,10 +1071,17 @@ void S9xSetPPU (uint8 Byte, uint16 Address)
 /******************************************************************************/
 uint8 S9xGetPPU (uint16 Address)
 {
+#ifndef NO_OPEN_BUS
  	uint8 byte = OpenBus;
-
+#else
+	uint8 byte = 0; // Arbitrarily chosen value [Neb]
+#endif
 	if(Address<0x2100)//not a real PPU reg
+#ifndef NO_OPEN_BUS
 		return OpenBus; //treat as unmapped memory returning last byte on the bus
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
     if (Address <= 0x2190)
     {
  	switch (Address)
@@ -1086,18 +1093,34 @@ uint8 S9xGetPPU (uint16 Address)
   #ifdef DEBUGGER
   	    missing.oam_address_read = 1;
   #endif
-			return OpenBus;
+#ifndef NO_OPEN_BUS
+		return OpenBus;
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
 
 	case 0x2104:
 	case 0x2105:
 	case 0x2106:
+#ifndef NO_OPEN_BUS
 		return PPU.OpenBus1;
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
 	case 0x2107:
+#ifndef NO_OPEN_BUS
 		return OpenBus;
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
 	case 0x2108:
 	case 0x2109:
 	case 0x210a:
+#ifndef NO_OPEN_BUS
 		return PPU.OpenBus1;
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
 	case 0x210b:
 	case 0x210c:
 	case 0x210d:
@@ -1107,8 +1130,14 @@ uint8 S9xGetPPU (uint16 Address)
 	case 0x2111:
 	case 0x2112:
 	case 0x2113:
-			missing.bg_offset_read = 1;
-			return OpenBus;
+#ifdef DEBUGGER
+		missing.bg_offset_read = 1;
+#endif
+#ifndef NO_OPEN_BUS
+		return OpenBus;
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
 
 	case 0x2114:
 #ifdef DEBUGGER
@@ -1116,15 +1145,27 @@ uint8 S9xGetPPU (uint16 Address)
 #endif
 	case 0x2115:
 	case 0x2116:
-			return PPU.OpenBus1;
+#ifndef NO_OPEN_BUS
+		return PPU.OpenBus1;
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
 
 	case 0x2117:
-			return OpenBus;
+#ifndef NO_OPEN_BUS
+		return OpenBus;
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
 
 	case 0x2118:
 	case 0x2119:
 	case 0x211a:
-			return PPU.OpenBus1;
+#ifndef NO_OPEN_BUS
+		return PPU.OpenBus1;
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
 
 	case 0x211b:
 	case 0x211c:
@@ -1135,25 +1176,45 @@ uint8 S9xGetPPU (uint16 Address)
 #ifdef DEBUGGER
 	    missing.matrix_read = 1;
 #endif
-			return OpenBus;
+#ifndef NO_OPEN_BUS
+		return OpenBus;
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
 
 	case 0x2121:
 	case 0x2122:
 	case 0x2123:
-			return OpenBus;
+#ifndef NO_OPEN_BUS
+		return OpenBus;
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
 
 	case 0x2124:
 	case 0x2125:
 	case 0x2126:
-			return PPU.OpenBus1;
+#ifndef NO_OPEN_BUS
+		return PPU.OpenBus1;
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
 
 	case 0x2127:
-			return OpenBus;
+#ifndef NO_OPEN_BUS
+		return OpenBus;
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
 
 	case 0x2128:
 	case 0x2129:
 	case 0x212a:
-			return PPU.OpenBus1;
+#ifndef NO_OPEN_BUS
+		return PPU.OpenBus1;
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
 
 	case 0x212b:
 	case 0x212c:
@@ -1164,7 +1225,11 @@ uint8 S9xGetPPU (uint16 Address)
 	case 0x2131:
 	case 0x2132:
 	case 0x2133:
-			return OpenBus;
+#ifndef NO_OPEN_BUS
+		return OpenBus;
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
 
 	case 0x2134:
 	case 0x2135:
@@ -1182,10 +1247,18 @@ uint8 S9xGetPPU (uint16 Address)
 #ifdef DEBUGGER
 	    missing.matrix_multiply = 1;
 #endif
-		return (PPU.OpenBus1 = Memory.FillRAM[Address]);
+		return (
+#ifndef NO_OPEN_BUS
+			PPU.OpenBus1 =
+#endif
+			Memory.FillRAM[Address]);
 	case 0x2137:
 		S9xLatchCounters(0);
+#ifndef NO_OPEN_BUS
 		return OpenBus;
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
 
 	case 0x2138:
 		// Read OAM (sprite) control data
@@ -1230,7 +1303,11 @@ uint8 S9xGetPPU (uint16 Address)
 #ifdef DEBUGGER
 	    missing.oam_read = 1;
 #endif
-		return (PPU.OpenBus1 = byte);
+		return (
+#ifndef NO_OPEN_BUS
+			PPU.OpenBus1 =
+#endif
+			byte);
 
 	case 0x2139:
 		// Read vram low byte
@@ -1275,7 +1352,9 @@ uint8 S9xGetPPU (uint16 Address)
 				IPPU.FirstVRAMRead = FALSE;
 			}
 #endif
+#ifndef NO_OPEN_BUS
 			PPU.OpenBus1 = byte;
+#endif
 			break;
 	case 0x213A:
 		// Read vram high byte
@@ -1319,7 +1398,9 @@ uint8 S9xGetPPU (uint16 Address)
 				IPPU.FirstVRAMRead = FALSE;
 			}
 #endif
+#ifndef NO_OPEN_BUS
 			PPU.OpenBus1 = byte;
+#endif
 			break;
 
 	case 0x213B:
@@ -1333,7 +1414,11 @@ uint8 S9xGetPPU (uint16 Address)
 		byte = PPU.CGDATA [PPU.CGADD] & 0xff;
 
 	    PPU.CGFLIPRead ^= 1;
-	    return (PPU.OpenBus2 = byte);
+	    return (
+#ifndef NO_OPEN_BUS
+		PPU.OpenBus2 =
+#endif
+		byte);
 	    
 	case 0x213C:
 	    // Horizontal counter value 0-339
@@ -1341,10 +1426,19 @@ uint8 S9xGetPPU (uint16 Address)
 	    missing.h_counter_read = 1;
 #endif
 	    if (PPU.HBeamFlip)
-		byte = (PPU.OpenBus2 & 0xfe) | ((PPU.HBeamPosLatched >> 8) & 0x01);
+		byte =
+#ifndef NO_OPEN_BUS
+			(PPU.OpenBus2 & 0xfe)
+#else
+			0 // Arbitrarily chosen value [Neb]
+#endif
+			| ((PPU.HBeamPosLatched >> 8) & 0x01);
+
 	    else
 		byte = (uint8)PPU.HBeamPosLatched;
+#ifndef NO_OPEN_BUS
             PPU.OpenBus2 = byte;
+#endif
 	    PPU.HBeamFlip ^= 1;
 	    break;
 
@@ -1354,10 +1448,18 @@ uint8 S9xGetPPU (uint16 Address)
 	    missing.v_counter_read = 1;
 #endif
 	    if (PPU.VBeamFlip)
-                byte = (PPU.OpenBus2 & 0xfe) | ((PPU.VBeamPosLatched >> 8) & 0x01);
+                byte =
+#ifndef NO_OPEN_BUS
+			(PPU.OpenBus2 & 0xfe)
+#else
+			0 // Arbitrarily chosen value [Neb]
+#endif
+			| ((PPU.VBeamPosLatched >> 8) & 0x01);
 	    else
                 byte = (uint8)PPU.VBeamPosLatched;
+#ifndef NO_OPEN_BUS
             PPU.OpenBus2 = byte;
+#endif
 	    PPU.VBeamFlip ^= 1;
 	    break;
 
@@ -1366,14 +1468,22 @@ uint8 S9xGetPPU (uint16 Address)
 	    FLUSH_REDRAW ();
 
 	    //so far, 5c77 version is always 1.
-		return (PPU.OpenBus1 = (Model->_5C77 | PPU.RangeTimeOver));
+		return (
+#ifndef NO_OPEN_BUS
+			PPU.OpenBus1 =
+#endif
+			(Model->_5C77 | PPU.RangeTimeOver));
 
 	case 0x213F:
 	    // NTSC/PAL and which field flags
 	    PPU.VBeamFlip = PPU.HBeamFlip = 0;
             //neviksti found a 2 and a 3 here. SNEeSe uses a 3.
             //XXX: field flags not emulated
-	    return ((Settings.PAL ? 0x10 : 0) | (Memory.FillRAM[0x213f] & 0xc0)| Model->_5C78) | (~PPU.OpenBus2 & 0x20);
+	    return ((Settings.PAL ? 0x10 : 0) | (Memory.FillRAM[0x213f] & 0xc0)| Model->_5C78)
+#ifndef NO_OPEN_BUS
+			| (~PPU.OpenBus2 & 0x20)
+#endif
+			;
 
 	case 0x2140: case 0x2141: case 0x2142: case 0x2143:
 	case 0x2144: case 0x2145: case 0x2146: case 0x2147:
@@ -1403,7 +1513,7 @@ uint8 S9xGetPPU (uint16 Address)
 	    {
 #ifdef CPU_SHUTDOWN
 //		CPU.WaitAddress = CPU.PCAtOpcodeStart;
-#endif	
+#endif
 		if (SNESGameFixes.APU_OutPorts_ReturnValueFix &&
 		    Address >= 0x2140 && Address <= 0x2143 && !CPU.V_Counter)
 		{
@@ -1457,10 +1567,18 @@ uint8 S9xGetPPU (uint16 Address)
 	case 0x2181:
 	case 0x2182:
 	case 0x2183:
-			return OpenBus;
+#ifndef NO_OPEN_BUS
+		return OpenBus;
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
 
-		  default:
-			return OpenBus;
+	default:
+#ifndef NO_OPEN_BUS
+		return OpenBus;
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
 	}
     }
     else
@@ -1474,15 +1592,23 @@ uint8 S9xGetPPU (uint16 Address)
 	    {
 	    case 0x21c2:
 			if(Model->_5C77 ==2)
-		        return (0x20);
+		        	return (0x20);
 
 			//	fprintf(stderr, "Read from $21c2!\n");
-				return OpenBus;
+#ifndef NO_OPEN_BUS
+			return OpenBus;
+#else
+			return 0; // Arbitrarily chosen value [Neb]
+#endif
 	    case 0x21c3:
-				if(Model->_5C77 ==2)
+			if(Model->_5C77 ==2)
 			        return (0);
 			//	fprintf(stderr, "Read from $21c3!\n");
-				return OpenBus;
+#ifndef NO_OPEN_BUS
+			return OpenBus;
+#else
+			return 0; // Arbitrarily chosen value [Neb]
+#endif
 	    case 0x2800:
 		// For Dai Kaijyu Monogatari II
 		if (Settings.SRTC)
@@ -1498,12 +1624,20 @@ uint8 S9xGetPPU (uint16 Address)
 		    S9xMessage (S9X_TRACE, S9X_PPU_TRACE, String);
 		}
 #endif
-				return OpenBus;
+#ifndef NO_OPEN_BUS
+		return OpenBus;
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
 	    }
 	}
 	
 	if (!Settings.SuperFX)
-			return OpenBus;
+#ifndef NO_OPEN_BUS
+		return OpenBus;
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
 #ifdef ZSNES_FX
 	if (Address < 0x3040)
 	    byte = S9xSuperFXReadReg (Address);
@@ -2165,7 +2299,11 @@ uint8 S9xGetCPU (uint16 Address)
 				S9xMessage (S9X_TRACE, S9X_PPU_TRACE, String);
 			}
 #endif
-			return OpenBus;
+#ifndef NO_OPEN_BUS
+		return OpenBus;
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
 
 		}
 //		return (Memory.FillRAM [Address]);
@@ -2189,7 +2327,11 @@ uint8 S9xGetCPU (uint16 Address)
 	  case 0x420d:
 	  case 0x420e:
 	  case 0x420f:
+#ifndef NO_OPEN_BUS
 		return OpenBus;
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
 
 	  case 0x4210:
 #ifdef CPU_SHUTDOWN
@@ -2198,7 +2340,11 @@ uint8 S9xGetCPU (uint16 Address)
 		byte = Memory.FillRAM[0x4210];
 		Memory.FillRAM[0x4210] = Model->_5A22;
 		//SNEeSe returns 2 for 5A22 version.
-		return ((byte&0x80)|(OpenBus&0x70)|Model->_5A22);
+		return ((byte&0x80)
+#ifndef NO_OPEN_BUS
+			|(OpenBus&0x70)
+#endif
+			|Model->_5A22);
 
 	  case 0x4211:
 		byte = (CPU.IRQActive & (PPU_V_BEAM_IRQ_SOURCE | PPU_H_BEAM_IRQ_SOURCE)) ? 0x80 : 0;
@@ -2207,7 +2353,9 @@ uint8 S9xGetCPU (uint16 Address)
 		CLEAR_IRQ_SOURCE (PPU_V_BEAM_IRQ_SOURCE | PPU_H_BEAM_IRQ_SOURCE);
 
 		// Maybe? Register Scan indicated open bus...
+#ifndef NO_OPEN_BUS
 		byte |= OpenBus&0x3f;
+#endif
 
 		return (byte);
 
@@ -2216,7 +2364,11 @@ uint8 S9xGetCPU (uint16 Address)
 #ifdef CPU_SHUTDOWN
 		CPU.WaitAddress = CPU.PCAtOpcodeStart;
 #endif
-		return (REGISTER_4212()|(OpenBus&0x3E));
+		return (REGISTER_4212()
+#ifndef NO_OPEN_BUS
+			|(OpenBus&0x3E)
+#endif
+			);
 
 	  case 0x4213:
 		// I/O port input - returns 0 wherever $4201 is 0, and 1 elsewhere
@@ -2401,7 +2553,11 @@ uint8 S9xGetCPU (uint16 Address)
 			return Memory.FillRAM[Address];
 		}
 
+#ifndef NO_OPEN_BUS
 		return OpenBus;
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
     }
 //    return (Memory.FillRAM[Address]);
 }
@@ -2469,8 +2625,10 @@ void S9xResetPPU ()
 	PPU.OAMPriorityRotation = 0;
 	PPU.OAMWriteRegister = 0;
 	PPU.RangeTimeOver = 0;
+#ifndef NO_OPEN_BUS
 	PPU.OpenBus1 = 0;
 	PPU.OpenBus2 = 0;
+#endif
 
 	PPU.OAMFlip = 0;
 	PPU.OAMTileAddress = 0;
@@ -2665,8 +2823,10 @@ void S9xSoftResetPPU ()
 	PPU.OAMPriorityRotation = 0;
 	PPU.OAMWriteRegister = 0;
 	PPU.RangeTimeOver = 0;
+#ifndef NO_OPEN_BUS
 	PPU.OpenBus1 = 0;
 	PPU.OpenBus2 = 0;
+#endif
 
 	PPU.OAMFlip = 0;
 	PPU.OAMTileAddress = 0;
diff --git a/source/ppu.h b/source/ppu.h
index 5a889ef..6daf473 100644
--- a/source/ppu.h
+++ b/source/ppu.h
@@ -266,8 +266,10 @@ struct SPPU {
     // XXX Do these need to be added to snapshot.cpp?
     uint16 OAMWriteRegister;
     uint8 BGnxOFSbyte;
+#ifndef NO_OPEN_BUS
     uint8 OpenBus1;
     uint8 OpenBus2;
+#endif
 };
 
 #define CLIP_OR 0
diff --git a/source/sa1.cpp b/source/sa1.cpp
index 39b08bb..eb10d33 100644
--- a/source/sa1.cpp
+++ b/source/sa1.cpp
@@ -228,14 +228,23 @@ uint8 S9xSA1GetByte (uint32 address)
 #ifdef DEBUGGER
 //	printf ("R(B) %06x\n", address);
 #endif
+#ifndef NO_OPEN_BUS
         return OpenBus;
+#else
+		return 0; // Arbitrarily chosen value [Neb]
+#endif
     }
 }
 
 uint16 S9xSA1GetWord (uint32 address)
 {
+#ifndef NO_OPEN_BUS
     OpenBus = S9xSA1GetByte (address);
     return (OpenBus | (S9xSA1GetByte (address + 1) << 8));
+#else
+	uint8 Split = S9xSA1GetByte (address);
+	return (Split | (S9xSA1GetByte (address + 1) << 8));
+#endif
 }
 
 void S9xSA1SetByte (uint8 byte, uint32 address)