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Stunt Race 3D Demo (PD).gb graphic glitches during the gameplay #153

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benderscruffy opened this issue Jan 19, 2025 · 4 comments
Open

Stunt Race 3D Demo (PD).gb graphic glitches during the gameplay #153

benderscruffy opened this issue Jan 19, 2025 · 4 comments
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bug Something isn't working gb Game Boy / Game Boy Color

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@benderscruffy
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@jsgroth jsgroth added bug Something isn't working gb Game Boy / Game Boy Color labels Jan 19, 2025
@jsgroth
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jsgroth commented Jan 19, 2025

Looks like a CPU/PPU timing issue. It works fine if I don't block VRAM writes that occur on dot=84, technically during the first M-cycle of PPU mode 3:

Image

Allowing these writes through also seems to partially fix the issue in #33, but I think it's going to be hard to completely fix that one without solving the underlying timing issue.

jsgroth added a commit that referenced this issue Jan 19, 2025
@jsgroth
[GB] don't block VRAM writes that occur on dot=84 (#153)
e0e20ed 
this is mainly a hack to work around what seems to be an unrelated timing issue, but it fixes glitched graphics in the Stunt Race FX GB demo
@jsgroth jsgroth added the fixed-next-release Fixed on master, will go into next release label Jan 19, 2025
@benderscruffy
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benderscruffy commented Jan 20, 2025 •
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sorry but this is broken on hardware aswell
just tried this on my gameboy

@jsgroth
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jsgroth commented Jan 23, 2025

Interesting, was that on an original Game Boy or a GBC/GBA? There are some very slight PPU timing differences between the two (which I don't currently emulate), so I would believe it if this works on one but not the other.

@benderscruffy
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this was on a GBA with my everdrive card

@jsgroth jsgroth removed the fixed-next-release Fixed on master, will go into next release label Jan 23, 2025
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