Graphics corruption

[Zac67]

Insufficient power/voltage may well be a problem. Just like with probably most 'hard-core' users my C64 developed somewhat similar (horizontal) stripes after a few years. Later, I discovered that the PSU design was a problem and learned how to repair this fault.

Much later on, I repaired an unstable PET that wouldn't work reliably after a RAM expansion. Raising the PSU voltage a bit plus using thicker leads did the trick.

Check the exact voltages on the RAM chips and on the PSU output. If there's a larger discrepancy you need to enforce the power traces on the board for better distribution. If the level is too low (<<4,95V) you need to beef up the PSU or replace it.

PS: Listen to Karlos: that feeble floppy connector can't seriously power all that hardware...

[Zac67]

Im using a tweaked bvisionppc 'monitor', that goes up to 76khz -is that a problem? I remember tweaking that monitor a little while before the trouble started.

Overclocking the video memory bus or the video chip can also cause problems like these. Can't you just try with a lower res?

[Zac67]

If a clean reinstall of CGX doesn't work, you might consider a physical strip and rebuild, cleaning all the connectors thoroughly of any grime and dust.

Don't think there's any connector involved here, the distortion wouldn't be so static. It's a problem on the gfx card, but since it's with several ones you can rule out a hardware defect. It's either power related, overclocked RAM/chip/RAMDAC or a 'simple' software problem.

I'd leave the installation as is and do a parallel, clean install (separate disk, partition or just system folders). Starting with a basic setup and working your way up from there will definitely tell you where the trouble starts.

[Zac67]

Incidentally, have you made sure it's not the monitor? Those digital displays can develop pretty strange defects at times...