Post #2762162
2026-04-12 18:01 UTC
@pcy@icosahedron.website lol jesus. Specifics are hard but I guess the gist is if you swap background mode mid scanline the PPU in some cases uses wrong tile data due to a prefetch… happening? not happening? and the exact behavior is very timing dependent and also slightly weird?
Replies (1)
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@pcy@icosahedron.website 2026-04-12 18:05
@halcy@icosahedron.website it's because of a regular fetch not having already happened, and tile/map index/data latches being reset to 0 as a consequence it also upsets the horizontal-pixel-inside-a-tile counter, but in a way I don't fully understand. the T/Y graphic is declared as this in the demo: https://codeberg.org/PoroCYon/emulator-examination/src/branch/main/arm9/source/main_ntr.c#L37-L46 , but it gets displayed correctly 'somehow'. it's not just by rotating the columns around, some get duplicated and others don't get shown at all