mismatched as in ram amount or OEM?
If its mismatched ram I would not bother, by mismatched ram I mean a 8mb card and a 12mb card. You can sli an 8mb and 12mb card but it does not work all to well. Make sure the 8mb card is in the first PCI slot and the second is in the 12mb slot.
If its mismatched OEMs make sure both cards work by themselves and make sure the SLI cable is good.

Mismatched as in manufacturer. They're a Guillemot and a Trust Voodoo Dragon 2 The ram amount is 12MB each, but Guillemot have chips on a single side, while Trust have on both sides.
They work fine with more modern games, the troubles are with those who were developed for Voodoo1 and need patches.

arny91 wrote on 2020-05-12, 16:50:

Mismatched as in manufacturer. They're a Guillemot and a Trust Voodoo Dragon 2 The ram amount is 12MB each, but Guillemot have chips on a single side, while Trust have on both sides.
They work fine with more modern games, the troubles are with those who were developed for Voodoo1 and need patches.

ok so older voodoo1 games do not work, like tomb readier and mech warrior 2 for example?
OK if I recall there was a bat file you had to make to start up the games wit ha voodoo2
Here is a post I found talking about it Re: MechWarrior 2 | 3D card conversion files
You may just have to disable sli when playing some older games as well.

You're right, there was a bat file where you could set the SST environment variables to run those games, and I used that.
But since I added the second card, It's useless! The system hangs shortly after the DOS/4GW info dialog, and I can't
even press CTRL+C, It needs rebooting! I tried also with SST_SLIDETECT=0, with the same result.

arny91 wrote on 2020-05-12, 16:50:

Mismatched as in manufacturer. They're a Guillemot and a Trust Voodoo Dragon 2 The ram amount is 12MB each, but Guillemot have chips on a single side, while Trust have on both sides.
They work fine with more modern games, the troubles are with those who were developed for Voodoo1 and need patches.

Each chip is 512KB and for 12MB you need all spots on both sides to be populated, if one side is empty the Guillemont card should be 8MB and not 12MB...

Hi Tiido!
The Guillemot has no soldering pads for ram on the back!
It just has 12 V53C819HK27 chips on the front side, which are, indeed 512K x 16, that means 8Mbit -> 1 MB each chip.
The Trust has 24 V53C16258HK25 chips, which are 256K x 16, so 4Mbit -> 512KB each chip.
So both cards actually have 12MB even if the frequency rating is different, 90mhz for the 8Mbit chips and 100mhz for the 4Mbit.
I don't know if that's breaking compatibility with Voodoo1 games though.

Ok, that's interesting, I wasn't aware such chips exist. I now wonder if it would be possible to use these chips and create mystical 24MB cards out of regular ones 🤣

Each one of the Voodoo2's TMU supports up to 8MB of texture memory, so in theory you can double that, and reach 20MB total.
You can't upgrade frame buffer memory.

So I have to assume that compatibility with most Voodoo1 games is broken if the SLI is mismatched?

Try one of the mismatched drivers from Falconflys' old site. (Near the bottom of the page).

https://3dfxarchive.com/voodoo2.htm

Those "fast" ones you are using likely overclock the cards and that may be the cause of your instability.

Since Win32 drivers are running fine, and the only affected games are those who run under DOS, i took glide2x.ovl from those archives and replaced the one I had in C:\WINDOWS.
Different result followed, sometimes DOS/4GW won't even load, sometimes it keeps hanging right there, on another try a totally black screen did appear. But still no ingame.

Hi,
I found something new. DOS Glide games won't run anyway on my system. Having a SLI is the red herring, I removed one card, and discovered that I have to slow down the cpu to run older games.
There's a Pentium III 533B and a MS6199VA with Apollo Pro 133 (693A) chipset in here.
Found some info here:
Voodoo 2 difficulties.
I tried pciset but i have to find the device id of my chipset.

EDIT: Looks like the vendor/device id in the fixap133.bat file are the same as those I found with System Information Viever. When I run it, nothing seems to change. Tomb Raider 1 starts sometimes and hangs when drawing the first frame. You can actually see a faded half of the first frame drawed on the display, sometimes a bit less, and sometimes nothing at all, in many cases followed by a beep of the pc speaker.
Carmageddon and Splat Pack won't run at all. I noticed that this is happening both with the cpu running at full speed or slowed down to 400mhz.

I first tried this Voodoo2 SLI setup about 3 years ago with an ASUS P5A motherboard and AMD K6-2, but it was not detected, then I switched to MSI and P3, in this way the SLI was detected but older glide games, which were running fine on the former setup, weren't working anymore. I haven't turned on that machine in a very long time, and this is why I assumed that SLI was the culprit, but apparently I was wrong.