First post, by Deksor
Edit : first success with the Trident 8800CS mentioned in this post : Re: Let's improve video output quality of VGA ISA/VLB cards
As some of you may have noticed, the video quality of old video cards can vary to pretty good to absolutely mediocre.
But is it just "how it is" or can it be fixed ?
There are two major things involved into generating an image on these old video cards and that's the RAMDAC and the analogue circuit itself.
As root42 has shown here https://m.youtube.com/watch?v=9gROqRlejwA, changing the RAMDAC proves to make some changes in the way the card reacts to graphical effects and other things
For the analogue circuit it depends of the card and I don't have the knowledge to figure out what may or may not be wrong but I know I have a pretty good specimen for experimenting.
Here's a trident tvga8800br which must have one of the worst video quality I've ever seen on a video card.
Not only it suffers from various video artifacts, but there are also graphical glitches caused by the ramdac itself.
And I think that if I can get this one to look decent and share it with you, any card with a removable ramdac could be improved.
Some of the colors were simply not stable in the game pinball fantasies with the original ramdac (bt Bt476KP50).
By swapping the ramdac for another one salvaged from another card this problem was fixed.
However there are other problems left.
In some graphic modes there are jailbars and the brightness flickers a lot.
Obviously I tested another video card (I even used the same ramdac) and there was no such thing, so nothing in my setup is to blame except something in the card itself which must be in the analogue circuit.
To be fair I think I'm going to make a ramdac comparison first to check which model(s?) are the best.
I know the original chip used by IBM was an inmos chip, but having multiple sources to replace vintage chips will definitely help with the availability.
For the analogue circuit, I don't know. My knowledge in electronics is pretty basic
One thing I noticed looking at the trident card is that there are no capacitors connected to the rgb output whereas one of my old S3 cards does have three little ceramic caps. Maybe adding caps there would help with the flicker and the jailbars ? Maybe not ? Looking at the datasheet of the RAMDACs, none of the circuits I've seen on my video cards seem to match so I don't know how it's really supposed to be. I'll need help for that part.
I can't shoot photos right now to illustrate the things I've been dealing with so far but I will do later so stay tuned 😉
Trying to identify old hardware ? Visit Ultimate Hardware 2019 - Project's thread The Ultimate Hardware 2019 (UH19) project- a stason.org/TH99