Amiga 1200 corrupted graphics

[UnnamedCourier]

I got the bug to dig out my old A1200 recently, and one thing it's brought back into mind is some long standing bugs with graphics corruption it has in a very small number of games - workbench has always worked fine in all modes I've thrown at it.

I bought this computer second hand around 1994 and it's always had these issues as far as I know. It's a Rev 1D.1 board. In the idiocy of youth I assumed it was something to do with screen modes my TV at the time did not support so never got it repaired, but it's clear it's something more serious. I've got an A1230+ accelerator and various other gear installed, but this happens even without those devices.
Affected games:


Putty Squad

(Only had the demo then, but same thing happens in the final game)

(how the above screen should look


Capital Punishment



Skeleton Krew



Oddly all these games work, you just can't see what is going on. Putty Squad is perfect apart from the System 3 splash screen and title screen; in game it works fine. Capital punishment is totally corrupted ingame, but seems to play fine if you can somhow work out what is going on. Skeleton Crew is horribly corrupted but playable, with audio glitching occuring too. Interestingly if you move to certain parts of a level it displays perfectly in those area.
I also remember playing a demo of the Lion King back in the day that had minor corruption occuring.

The above are all AGA games, not sure if it's just AGA screen modes that are affected or just coincidence. Otherwise a good 100+ other games work fine.

Oh, a non-AGA game I found also affected:
The scrolling intro to Stardust is completely corrupted. Super Stardust does not have this problem.

This happens both from a VGA monitor connected, and also over RF.
Any ideas where to start to fix this? Bad Alice chip?

[CFou!]

have you try pre-installed version with WHDLOAD patch which fixes most of the problems related to the lack of backward compatibility with an accelerator card for example?

if you use disks version or installed without whdload patch, have you try to disable Cache in boot startup-menu (Hold - LMB and RMB then power on amiga see [ Show youtube player ])


for patches:
http://www.whdload.de/
http://www.whdload.de/games/CapitalPunishment.html
http://www.whdload.de/games/PuttySquad.html
http://www.whdload.de/games/SkeletonKrew.html

[UnnamedCourier]

All of the above pictures were actually taken from running games in WHDLoad. That is not the cause of the issue and neither is any accelerator; these issues happened with games like Putty Squad running off floppy disk way before I had an accelerator or WHDLoad ever existed. This is definitey a hardware fault, not a software issue.

[redblade]

There is a system test rom that the hardware developers use to test their systems and take screenshots. I don't know what it's called sorry.

So you can display a 256 colour IFF or a HAM8 IFF okay in multiview?