Based on what you've encountered with it so far, I'd try reflowing the joints. A multimeter continuity test doesn't really ensure that the connections are good enough to perform well at high frequencies.
You could also try to check voltages on the card, but I don't know where to check those on a Voodoo. Do these cards have an onboard voltage regulator? If so, check that out as well as input voltages.

FIXED!! 🤣

The TMU RAS line wasn't connected to its RAM chips anymore.

The zero Ohm resistor R202 in the RAS line was entirely open. It seems to serve abolutely no purpose as its not even jumping across any traces. Maybe someone intended to put a series resistor there, but why isn't there such a thing in the FBI RAS line then? Its solder joints were actually good, and reflowing them did not make any difference. I bridged it and this card now freaking works.

Now how big were the odds for such a fault 😉

Weird. Good job finding that.

shamino wrote on 2020-06-21, 06:13:

Weird. Good job finding that.

Not everything is quite right yet, though. The Tombraider demo works abolutely flawlessly every time. However everything I've tried in Win98 as well as 3dfx Descent 2 in DOS still gives me the yellow screen. I've swapped the K6-2 400 for a P133 without any effect.

I'm going to try a different mainboard now.

watz wrote on 2020-06-21, 11:02:

I'm going to try a different mainboard now.

I'm going crazy. The card works fine in a P3B board (tried Quake2, Unreal, 3D Mark 99). It does not work in another VX based board I got. That gives the following results:

Asus P55T2P4 (430HX), K6-2 @400 / Pentium @133, 32 MB EDO, MGA450 PCI:
- DOS Tomb Demo ok
- anything Windows based = yellow screen

Asus P3B (440BX), Pentium 3 @566, 256MB SDRAM, MGS450 PCI:
- DOS Tomb Demo ok
- anything Windows based ok

Expert 8661 (430VX), K6-2 @450, 32 MB EDO, MGA450 PCI:
- DOS Tomb Demo ok
- anything Windows based = green or red screen

It has to be something else. I'm thinking of bad caps on the Voodoo card, although it has only tantalums. Or maybe a power supply issue.

Try a different main video card if You have one.
If it works perfectly on the P3 system then it won't be the voodoo1 that is the problem.
Maybe it's not properly switching between video cards. Software/driver issues?

Imperious wrote on 2020-06-21, 13:27:

Try a different main video card if You have one.
If it works perfectly on the P3 system then it won't be the voodoo1 that is the problem.
Maybe it's not properly switching between video cards. Software/driver issues?

Thats the thing: I've used the exact same SD card to boot all three boards. Surprisingly, when I switched from the 430HX to the 440 BX board, Win98 does not install any new drivers at all. It just boots and works, including the Voodoo. However when switching to the 430VX board, Win98 does install a few new drivers. I've tried various Voodoo drivers but the symptom is always the same (yellow most times on the Hx board and green, red or blue on the VX board). I also get that screen immediately when running DxDiag, which is handy for testing. Except on the P3 board of course, where DxDiag works totally fine with the Voodoo.

I've already tried a different primary card (PCI ATI Rage II), because I suspected the MGA450 is too new and causing trouble. I'll dig out an old ISA card tomorrow. Maybe I have bad luck and both cards cause issues. I can also rule out power supply and RAM issues. I've tried a P133 and lower bus speeds even. I've added additional caps to the board. Nothing changes on the Socket 7 boards.

I also got that yellow screen once when I executed Descent 2 d2_3dfx.exe in DOS, where I get a black screen otherwise. So I think its not directly related to Windows or its drivers. The tomb raider demo is always working on any board, so it probably initializes the card differently. All other things seem to initialize the card in a way that makes it crash on both my Socket 7 boards.

I've tried the ISA card in the VX board and the crash is still there. So I can also rule out the other two PCI main video cards as cause. Manually reassigning PCI memory resources of the Voodoo didn't do anything either.

Finally, I switched back to the P3 board again and the Voodoo is working perfectly there in Win98 as before. I'm all out of ideas as to why it does not work in both of my socket 7 boards besides DOS. And I know I had a Voodoo 1 running in that specific 430VX board in 1997. Maybe I'll try Win95 OSR2.

DOS Descent 2 (d2voodoo.exe and d2_3dfx.exe) is actually giving me a black screen even on the P3. As it never actually worked anywhere for me, I'm thinking that something is just wrong with the installation.

It may be that some capacitor(s) on the voltage line are busted and one board has much better power regulation while the other does not?

appiah4 wrote on 2020-06-22, 08:23:

It may be that some capacitor(s) on the voltage line are busted and one board has much better power regulation while the other does not?

Yes thats what I was thinking, too, and thats why I've put some extra caps on the Voodoo and changed the PSU. The card itself has only tantalum and ceramic caps which typically do not fail. But the same should be true for zero Ohm resistors in data lines...

For some mysterious reason, the card started working on the 430HX+P133 board in Win98 without any issues there. I've tried everything to get it back into the faulty state (reseating, different slots, reverting Bios options,...),
but it refuses to fail again in Windows. Currently, it works as good as in the P3 board there.

It still crashes in DOS though (except Tombraider, that always works). I've figured out that when the yellow/black/green/whatever color crash hang occurs, you can still take a look the program output by plugging in the VGA cable into the main video card. Both TES Redguard "rgfx.exe" and Descent "d2_3dfx.exe"/"d2voodoo.exe" crash right after switching the VGA output to the Voodoo with a DOS4GW general protection fault. TES Redguard "rgfx.exe" runs fine when started in Windows. "de_3dfx.exe"/"d2voodoo.exe" do still crash there.

I'll try Win95OSR2 next. Maybe these (DOS) games don't like something in my Win98SE installation.

I just fixed an old Socket A board by recapping it. Its got a Sempron 2300+ @1567Mhz. installed. Just for fun, I plugged in the Voodoo 1 and booted the same SD card into Win98 DOS mode, not expecting much to work due to the CPU speed.

Tombraider demo works fine as usual. Descent 2 executables lock up again. But the TES Redguard rgfx.exe works here! Strange. I can't really make out a pattern.