Strange behavior in burned game

Strange behavior in burned game
by Computolio on 2006-02-01 (#8959)

I burned Ufouria to a NES cart and it seems to work fine, at least for a while. After 20-40 minutes of gameplay, however, some of the background tiles start freaking out. I'm getting a sort of "shimmering" effect.

Any idea what's causing this?

by tepples on 2006-02-01 (#8960)

Have you tried cleaning the CHR side of the cart contacts with rubbing alcohol? Are you sure you did a good soldering job on the CHR chip?

by kyuusaku on 2006-02-02 (#9011)

I think there was a thread about this already. Kevtris mentioned the PGM pin and how different EPROMs require different voltage on it to be stable, try reversing your level.

by kevtris on 2006-02-06 (#9218)

kyuusaku wrote:
I think there was a thread about this already. Kevtris mentioned the PGM pin and how different EPROMs require different voltage on it to be stable, try reversing your level.

Yes, PGM *must* be pulled high when it is not being used. Also, VPP must be pulled high. Never "float" (leave disconnected) either or ground either. The only exception is when VPP is shared with a control signal such as /CE or similar. In that case, the chip has circuitry to handle it.

I have seen some chips do really odd things when VPP was just floated. Stuff like the ROM would work but if you moved your hand near it, the code running would crash (due to noise pickup from your body, etc).