Bad cart connection makes NES display all 256 tiles

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Dwedit
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Bad cart connection makes NES display all 256 tiles

Post by Dwedit »

I saw a game have a bad cartridge connection, and it looked like it was treating the low 8 address bits of a nametable tile fetch as the nametable tile byte itself. Would any specific pin being connected badly cause this fault?

Screenshot:
faria-bad.png
It also went in and out of glitchiness, example animated GIF: (click to play, 195KB)
faria-bad2.gif
Here come the fortune cookies! Here come the fortune cookies! They're wearing paper hats!
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Ben Boldt
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Re: Bad cart connection makes NES display all 256 tiles

Post by Ben Boldt »

I am guessing CIRAM /CE or PPU /A13, which (in the case of Faria) the cart connects directly together. With this connection open, nametable accesses would then be open bus, which I think would carry over the incrementing nametable addresses as data sequentially like that. Since your pattern tables still operate from CHR-ROM in the cart, the graphic data can still display.
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rainwarrior
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Re: Bad cart connection makes NES display all 256 tiles

Post by rainwarrior »

That looks pretty neat.
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