Use correct VRAM transfer mode for savestates

tewtal / sm_practice_hack

Super Metroid Practice Hack

The Unlicense

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Use correct VRAM transfer mode for savestates #203

Closed NobodyNada closed 6 months ago

NobodyNada commented 6 months ago

We set the high bit of $2115 to 0, which instructs the PPU to increment the VRAM word address after writing the low data byte. However, the DMA transfer writes low bytes first, then high bytes. This means the high byte of the first word of a transfer was being skipped, leading to an occasional glitchy tile. Setting the mode bit to 1 instead fixes the issue.

InsaneFirebat commented 6 months ago

Nice. That's probably the bug total mentioned a long time ago but I couldn't make any sense of it at the time.

InsaneFirebat commented 6 months ago

Merged with #202