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| author | Nebuleon Fumika | 2012-12-20 18:10:38 -0500 |
|---|---|---|
| committer | Nebuleon Fumika | 2012-12-20 18:14:24 -0500 |
| commit | 80858801300a2f48ad250721a79ebc7b1b0aba92 (patch) | |
| tree | a64d661a5e40b759a083a653841dff2ae82fa130 /source/cpuops.cpp | |
| parent | 83426640a6079021815e611ff0519d27ca3f9ce4 (diff) | |
| download | snes9x2005-80858801300a2f48ad250721a79ebc7b1b0aba92.tar.gz snes9x2005-80858801300a2f48ad250721a79ebc7b1b0aba92.tar.bz2 snes9x2005-80858801300a2f48ad250721a79ebc7b1b0aba92.zip | |
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.
Diffstat (limited to 'source/cpuops.cpp')
| -rw-r--r-- | source/cpuops.cpp | 36 |
1 files changed, 32 insertions, 4 deletions
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); |