Hm, the PPU tests I just wrote are displaying the wrong pictures in MESS ... maybe you can take a look?

[Linked Image from byuu.org]
(should fade in and out)

[Linked Image from byuu.org]
(should scroll vertically)

The first one shows up as a solid white screen, and the second isn't showing the zig-zag patterns. Test ROM files are here:

http://byuu.org/temp/test_ppu.zip

Have fun wink