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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/sa1.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/sa1.cpp')
| -rw-r--r-- | source/sa1.cpp | 9 |
1 files changed, 9 insertions, 0 deletions
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) |