pentiumspeed wrote on 2023-06-01, 22:55:

Corruption is memory speed or memory had degraded. These chips you have is 4 of junk quality memory chips and other 4 chips made by IBM could be 100ns or 120ns that were made for IBM made 256K modules rated at 120ns or 100ns.

Unfortunately ram is soldered on this video card. My best advice is to bend period correctness a bit on your nostalgic computer is to replace the video card with another of bit better. I suggest get another trident video card 8900D with 1MB installed. It will say trident on start up still.

Cheers,

Thanks for your advice! However, what is more important to me is neither the RESULT of getting 800x600-256 mode output to work nor the so called period correctness. I can easily plug in my idle S3Trio64V+ and get the way better performance or, like you have said, to buy a 8900D. But I prefer to figure out the problem itself, to get deeper understanding about these old hardwares/softwares. This process itself and the knowledge to solve all these issue is exactly what I want. Or I'd not bother fiddling all these old stuff.

This corruption problem is definitely because of the memory chips on the card as thought of earlier, nothing short of replacing them will get you working high resolutions. The chips simply are too slow. It sounsd like modifications are not an option to the particular card so you will have to live with the low resolutions. For what it is worth, the higher ones are very low performance on this card anyway and I don't use them on any of my ISA Tridents, I found the extra desktop space in Windows is not really worth the dramatic reduction in performance with these cards.

Sorry to revamp such an old topic. However, I have a TVGA8900D with 1MB and I can't get Hi-Color under any resolution in Windows 95.
I know that the monitor actually supports up to 1024x768x32bit however, I can´t get even 640x480 with High color (the best I can do is 1024x768 256 colors)
Does someone has any idea?
I tried with SVM.EXE under DOS and it seems that it accepted 800x600 Hi Color mode, but not on windows.

caiot5 wrote on 2024-01-23, 06:44:

Sorry to revamp such an old topic. However, I have a TVGA8900D with 1MB and I can't get Hi-Color under any resolution in Windows […]
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Sorry to revamp such an old topic. However, I have a TVGA8900D with 1MB and I can't get Hi-Color under any resolution in Windows 95.
I know that the monitor actually supports up to 1024x768x32bit however, I can´t get even 640x480 with High color (the best I can do is 1024x768 256 colors)
Does someone has any idea?
I tried with SVM.EXE under DOS and it seems that it accepted 800x600 Hi Color mode, but not on windows.

What is the RAMDAC chip on the card ? Does it support more than 256 colours ?

I wasn't able to identify which chip is the RAMDAC in my card, so as it is beyond my knowledge, I'm attaching a picture of the card:

KDA0476 is a standard VGA RAMDAC, limited to 256 colors.

Grzyb wrote on 2024-01-23, 16:01:

KDA0476 is a standard VGA RAMDAC, limited to 256 colors.

I see, so this is the best we can get.
Do you have any idea of why the SVM.EXE seems to be applying hi-color under DOS? Or is it just placebo, like it always 'seem' to set the resolution, even that it doesn't support?

caiot5 wrote on 2024-01-23, 16:20:

Do you have any idea of why the SVM.EXE seems to be applying hi-color under DOS? Or is it just placebo, like it always 'seem' to set the resolution, even that it doesn't support?

How does that mode look like?
I would expect some garbage, or a completely different mode from the one it's trying to set.

Anyway, it's possible that SVM doesn't attempt to detect the RAMDAC type, and/or it's a version for different card.

Grzyb wrote on 2024-01-23, 16:30:

How does that mode look like?
I would expect some garbage, or a completely different mode from the one it's trying to set.

Anyway, it's possible that SVM doesn't attempt to detect the RAMDAC type, and/or it's a version for different card.

By the 'preview mode' from the SVM.EXE, it looks the same as it does on 256 colors, I don't see any garbage at all (apart from the fact that it does look weird even in 256 colors).
But yeah, maybe it's just ignoring the RAMDAC type and trying best effort to display something (and not really switching to Hi-Color mode), but I asked just out of curiosity.
Anyway, thanks guys!