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GameINI: Add a game patch to work around dcache issue (RX4E4Z) #6417

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merged 1 commit into from Mar 2, 2018

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@leoetlino
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leoetlino commented Mar 2, 2018

Work around a dcache issue by preventing the game from doing
something pointless.

The game's DVD read function writes 0x87654321 to the entire read
buffer and 0x12345678 to the last 4 bytes. It then calls DVDReadAsync()
and without waiting for the read to complete at all, it checks if the
last 4 bytes are still 0x12345678. If they are, then the game fails.

The check always passes on console because DVDReadAsync() calls
issueCommand(), which calls DCInvalidateRange(read_buffer) (dcbi).

Dolphin cannot emulate this without an extremely significant
performance hit (3-7x according to JMC).

GameINI: Add a game patch to work around dcache issue (RX4E4Z)
Work around a dcache issue by preventing the game from doing
something pointless.

The game's DVD read function writes 0x87654321 to the entire read
buffer and 0x12345678 to the last 4 bytes. It then calls DVDReadAsync()
and without waiting for the read to complete at all, it checks if the
last 4 bytes are still 0x12345678. If they are, then the game fails.

The check always passes on console because DVDReadAsync() calls
issueCommand(), which calls DCInvalidateRange(read_buffer) (dcbi).

Dolphin cannot emulate this without an extremely significant
performance hit.
@JMC47

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JMC47 commented Mar 2, 2018

Fixes Casper's Scare School: Spooky Sports Day.

Also it runs at like 600 FPS so maybe we can have dcache and this game run fine.

@Helios747 Helios747 merged commit 619449a into dolphin-emu:master Mar 2, 2018

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