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MMU: Clarify masking on gather pipe address

This commit is contained in:
Pokechu22 2022-07-21 14:18:35 -07:00
parent 1c833ddc3c
commit c06f203e98
1 changed files with 9 additions and 2 deletions
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11
Source/Core/Core/PowerPC/MMU.cpp
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@ -283,8 +283,15 @@ static void WriteToHardware(u32 em_address, const u32 data, const u32 size)
}
// Check for a gather pipe write.
// Note that we must mask the address to correctly emulate certain games;
// Pac-Man World 3 in particular is affected by this.
//
// Note that we must mask the address to correctly emulate certain games; Pac-Man World 3
// in particular is affected by this. (See https://bugs.dolphin-emu.org/issues/8386)
//
// Note that the PowerPC 750CL manual says (in section 9.4.2 Write Gather Pipe Operation on page
// 327): "A noncacheable store to an address with bits 0-26 matching WPAR[GB_ADDR] but with bits
// 27-31 not all zero will result in incorrect data in the buffer." So, it's possible that in some
// cases writes which do not exactly match the masking behave differently, but Pac-Man World 3's
// writes happen to behave correctly.
if (flag == XCheckTLBFlag::Write &&
(em_address & 0xFFFFF000) == GPFifo::GATHER_PIPE_PHYSICAL_ADDRESS)
{