NTDEC Family Game famiclone having weird PPU timing issues (NMI desync?)

[reedwolf]

I have this "Family Game" clone from NTDEC, it's a really neat clone, high compatibility, 50/60Hz switch integrated at the back. However, it has this weird PPU/NMI bug that causes more complex games (MMC3 and up usually) to have graphical glitches when the game tries to switch banks midframe.

After running the scanline test rom using an everdrive I got this result:


There's obviously something wrong but I don't really know.. maybe something related to the XTAL? 

On another clone, using UMC chips probably, the test passes:


This is how the clone looks inside:


Any help is appreciated

[TeTsUyUkI]

The TA chipset is know for not being 100% compatible like the UMC ones, you can allways swap those with other bootlegs or original ppu and cpu if you want 🙂