I was able to INF mod 56.64 drivers, anything older would throw an error during driver installation.
With 56.64, I have not noticed any difference in compatibility with various games (compared to 61.76 and 66.94). But I am not saying there isnt, I just didnt find/see it. The only noticeable difference to me was that the above mentioned artifacting was gone from 3DMark99.
I have also tried faking the Quadro as Geforce using Rivatuner, with various drivers, and there were noticeable FPS differences (both good and bad) so I would suggest anyone with a Quadro card to definitely try it on their own because your mileage might vary. Also notable is that VSYNC control and perhaps other things specifically for DirectX are unavailable in Quadro drivers, only in Geforce drivers. On the other hand Quadro drivers have 16x AA, Geforce only 8x. So if I decide to actually use a Quadro card in this build, I will probably make multiple small Windows partitions with various drivers that will better suit specific games.
Now some good news and bad news.
Good news is that I was able to solve the disk speed issue after installing RLoew SATA patch and doing some specific configuring in BIOS and Device Manager with his great help. The speed increased from 7MB/s to upto 215MB/s. Amazing. It also made the SATA CD-DVD drive work (which I didnt really pay attention to before).
Bad news is that the USB mouse lag issue is kind of back. It was always there but rather small so I didnt notice it at first. Basically the FPS drops when I type too fast on USB keyboard or move the USB mouse around too fast. Not by much (1-20FPS maybe) but it does interfere even with VSYNC on and results in small stuttering either way.
The 7950 GT has arrived now so I will be testing that soon. It is this model:
https://hexus.net/tech/reviews/graphics/7089- … -passive-512mb/
I have also tried installing color calibration ICC profile (.ICC file) via Nvidia setting panel which "worked", but somehow looked too bright compared to installing the same ICC on later Windows, and unfortunately did not even "stick" in games, just desktop. I have no problems forcing it in on Windows XP and higher in most games but trying to do this on Windows 98SE will be an issue it seems.