Graphics corruption

[rvo_nl]

For almost a year now I have barely touched my Amiga, because it suffers from a major graphics corruption issue, as can be seen below.
 

 

 
It doesnt look good.. The strange thing here is that my Workbench (OS3.9) screen itself shows up fine, as does early bootmenu / boot without startup-sequence. Its when I start diropus and perform some tasks that glitches start appearing. Usually just a pixel or two, then a line here and there, until it gets really bad and text on buttons and in menus becomes unreadable. When watching a serie of pictures, its even stranger: most pictures show up fine, but a few come out really bad, as can be seen in the second screenshot.
 
Now, I might sound like a complete moron, but believe me when I say its not a software issue. Years ago I did a very clean, well-documented installation of my machine, and havent touched anything since. And dont forget it ran fine for years before this issue came up. Also, I've tried many times commenting stuff out in my startup-sequence, all without effect.
 
I suspected the Bvision, too. So I replaced it, twice. I've tried 3 Bvisions now, and they all have this issue. Ofcourse I swapped the Bvision cable / PCB, too and tried reseating the card aswell as the ppc board many times.
 
It could be memory corruption, which Ive tried ruling out by running Memtest for a day, with 100% good result.
 
It could be the PPC or 68K CPU. (Surely hope not). Its very hard to test this, since I cannot display PAL and I need the PPC to use the Bvision.
 
It could be a power issue. I power the motherboard using a refurbished PSU that feeds power to the a1200 power connector, AND the floppy connector. I have new cables and new switches. But I read somewhere about a certain issue with sound output, when you only power the motherboard via the floppy connector? Well.. its hard to know for sure since my cabling is so messy/broken, but I think my sound output isnt working. Could this be an indication? I mean, are other components on the motherboard affected when power is only coming in over the floppy connector?
 
Last, it could be the motherboard. Ive replaced it 3 years ago, but perhaps I need to do it again.. ?
 
Any other ideas? Please help me out, I want my machine back!
 
Thanks for reading.

[rvo_nl]

Thanks for your replies so far. Perhaps I wasnt clear, Im not intentionally powering my system only over the floppy connector. Im just saying that perhaps the normal power supply is malfunctioning or 'jumps' a little bit. Im not sure this is even possible..

Im running the latest CGX4 with the very latest patches. I believe version number is then 4.3 rc5. 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.

[rvo_nl]

Hmm the more you people suggest, the more Im starting to think it IS a software issue after all.. Some nice things to try out, thanks again. Will report back soon

[rvo_nl]

Make sure any overclocking tooltypes are disabled in the monitor driver (hint: 2AIDEMREPYMNONAFADELLATSNII, MELTDOWN)

good one! they were enabled indeed, but disabling them didnt help at all.

[rvo_nl]

sigh.. I guess I will try. I really hope it helps, I've spent so much time installing my machine, the thought alone of reinstalling makes me feel down

Indeed, CGXMode is a pretty safe tool. The only thing you tell it before you can start tweaking the Monitor is the maximum khz your physical monitor supports.

[rvo_nl]

@freqmax, I will get back to you later on. You raised a valid point that I need to check out, together with Karlos' suggestions.

@TCMSLP that looks like a different problem, your artifacts are animated, whilst 'my' artifacts remain static. I also dont think there can be a heating issue, I get artifacts 30 seconds after doing a cold boot. And we had a proper winter here in Holland

@nscaleworld Thanks, but I dont want an AmigaOne and I love my Classic Machine. It will never be sold and I will never buy a different system. This is Amiga the way I want it.

[rvo_nl]

small update here. I tried running some AGA demo's on my tv set, worked fine, no artifacts at all. But there was no sound. More & more I suspected that this had something to do with it, so I removed all components from my machine, to see if sound would return. Not so. Then I reconnected all power cables, especially at the part where the PSU cables go into the a1200 mainboard. Suddenly I had sound output again! Probably a problem with the -12v line? Anyway, I couldnt wait to get everything back into the tower, do another positive sound test, and fire up Diropus. Well, even with sound working I still have the artifacts there I am quite afraid it has something to do with my ppc board. Next step will be a clean install of OS3.9 and CGX4, to see what happens then.

[rvo_nl]

I cant write applications.. otherwise I would.

@Karlos I did thoroughly clean connectors of bvision and power circuits. Sound is now at least always working, but the artifacts remain. Ive noticed they consist of 20 or-so lines spaced evenly across the screen. Everything they slice through becomes distorted. Most notably in menu's and interface buttons.

BTW, I never used serial so had no idea this was affected, too. My a1200 connects over PCMCIA.

Everything is now back in the tower and I've done a complete backup of the system, in case reinstalling doesnt help. I honestly dont know where to continue afterwards.. but we'll see.

[rvo_nl]

please allow me to stay on topic with another update. I didnt get round to reinstalling 3.9 and for some reason I couldnt get the 4.0 installer to work, so that will come later I did however find out something that is quite interesting:

I only have artifacts in 16 bit modes. 8 bit and 24 bit screens have no troubles. I did use CGXmode to change the configuration for the main 16 bit mode I use to something on the very safe side, but that didnt make any difference.

What do you people think is wrong here? PPC? Bvision? Software? I still fear for the PPC..

[rvo_nl]

they are fixed relative to the screen. they are always in the same position. even when I change the pixel clock for the mode myself. youre talking about the DAC, that is part of the bvision, right? how can it be that they all have the same issue? doesnt make sense.. interference? ..the kind that only appears in 16 bit modes? Im lost..

[rvo_nl]

thanks, Ive got 2 of those but they are not going to solve my trouble. I first need to rule out a software issue and for that I want to install OS4. No clue why this is not working though. Will report back when I made some progress there.

[rvo_nl]

well, I managed to install CGX4 (4.3 rc5) over a clean WB3.1 installation. Even with the default 56khz monitor, any resolution I tested had the same artifacts. Even in 8 bit. I guess I didnt spot the lines before, because of the few colours it uses. So every other screen except the workbench screen shows up garbled. Problem in certain memory range then? Must be Fastmem then, since all Bvisions have this problem?

Edit: seriously, please help me out. After spending some time with my machine I've noticed how much effort I put into it over the last few years. I really must get it working again and Im really eager to try out OS4.1 Classic. Any ideas are welcome. Anything on-topic, please..

[rvo_nl]

I had a similar problem once with a Picasso IV on an A2000, that had previously worked fine. Random garbage, that eventually progressed to lock-ups. After trying a million different things (and suspecting a dud PIV), it turned out to be something defective on the motherboard.

@damion interesting. did you have such 'garbage' also under RTG graphics modes? Because that is the strange part, everything on my a1200 board doesnt SEEM related to my bvision output, but maybe Im wrong. Anyway tonight I will try swapping both simm's for one out of my blizz1230. If that doesnt help, its either ppc, or mainboard.

@freqmax Im hoping to find someone nearby with a machine I can test my hardware on

@Zac67 yes, I have 2 identical monitors and swapped them around more than once, to rule out things.

[rvo_nl]

thanks both, for your help. there is only one way to test this, with another ppc and/or a1200 mainboard. I will try to find someone in my neighbourhood to help me out.

This night I tried some old 32MB Simm and also swapped Bvision, video cable and connector PCB around, all without result.

I had a very close look at the ppc board, it really looks fine, also under the heatsink I dont see any damage.

[rvo_nl]

tried that, didnt help.
 
HOWEVER..
 
take a look at this wonderful, glitch-free screen:
 

 
this is with another a1200 mainboard. When I put my own board in, and go to CGXmode, I get instant artifacts. So, case closed. I need a new motherboard!
 
no wait, I should have tested  a bit more. Now I have the exact same problem again, with a different motherboard. It happens less, but for example when I move the window in the picture above, the lines come back again. So, must be the PPC then. I guess that means its the end, coz Im sure as hell not replacing that one.