Alright, the caps arrived yesterday already (shipped from Texas on friday night! 😳) so I immediately recapped the Asus P2B and Voodoo3. I didn't look at the µF rating at all, just noted dimensions and picked the biggest cap that would fit on 😀
For the Asus board that meant:
1500µF -> 3300µF
1000µF -> 1500µF
1000µF -> 1200µF (between the ISA/PCI slots)
100µF -> 220µF
Also filled the empty spots with 1500µF, 6.3V caps.
On the Voodoo3 I replaced the 10µ electrolytics by 22µ solid polymer.
So, did it fix anything? The answer is yes.
- Screen shaking is pretty much gone, it's still there but I need a magnifying glass to see it now in 132x60 resolution.
- I am now able to run Doom with the Katmai 550 at 124 FSB and 1/1 AGP. Previously it would crash consistently in the same spot. Quake still pagefaults at this frequency though.
- With the Coppermine 800, it will now POST at 140 FSB and 1/1 AGP. Graphical artifacts are all over the place and it won't boot into DOS though.
- Booting with PC100 CL3 ram at 150MHz and 2-2-2 timings is now possible. Results in instant parity errors however when booting to DOS, but at least it doesn't start beeping outright. PC133 CL3 seems stable at this frequency.
All of these points are pretty minor, of course, but do show that system stability improved quite a bit.
On the other hand, the snow was still there, so I gave the 3dfx BIOS editor a try, as recommended by gerwin. (First of all, who the hell thought it was a good idea to place the Exit button (without confirmation!) where you'd normally expect the File menu!?)
I tried some different clock speeds and enabled triple buffering by default. At lower clocks it does start to do some really WEIRD things. For example, the text and background colours start changing randomly after every CLS in text mode. Yeah...
Higher clocks seem more stable somehow, and will allow slightly higher AGP clocks too. I managed to brick it a few times but that was easily fixed by booting with an S3 PCI card and reflashing.
I noticed that the BIOS I was using previously (v2.15.11-SD) had different RAM timings from what 3dfx recommended. These are:
tRAS = 7 (4 recommended)
tRC = 10 (7)
tRL = 0 (1)
I changed these to the recommended values. I was unable to set tBWL to 1 for some reason, it kept changing back to 2. I think this is a bug in the BIOS editor.
Clock speed was set to 1,1,68 (K,N,M) which results in 167.045MHz. Default was 1,1,58 (143.182MHz).
With these settings, 100MHz FSB and 2/3 AGP divider... The snow is gone! It comes back at higher FSB/AGP clocks, however, but this shows that it can be reduced and possibly even fixed completely using a modified BIOS. Will experiment some more with that.
edit: screen shaking appears to have returned with this BIOS 🙁... Still, it's not as bad as before.