Many mid to late 90s games were either Software or Glide. Some also had Direct3D, but the API was in its infancy and suffered from numerous bugs and performance issues.
Goes even further than that too -- many of them had no support for OpenGL or proper direct3d, and WILL NOT RUN even close to properly on ANY flavor of NT. 2K, XP? Faggedabaddit!
Some of them won't even work with later 3dfx cards like the Voodoo 3, 4 and 5. I've got a PCI 3, an AGP 3, and a AGP2x 5-5500, and NONE of them will for example work "properly" with the 3dfx release of Mechwarrior 2 Mercenaries. You HAVE to use a real V2.
Sometimes with some games to have proper working video you have to back out to older versions of the drivers such as those the card would have shipped with. That was more of a problem with the Banshee though -- a lot of games written for Voodoo II would work with the drivers off the disk the Banshee cards shipped with, but not if you updated to the latest release off of online. Even some directX games went tits up in that scenario such as Vampire:Redemption -- though that one using DirectX can be run just fine on modern systems.
Pretty much ALL the Microprose MechWarrior titles prior to 3 you HAVE to dial back to real Win98 and for them to run properly if at all -- and for many of them the best experience was on a genuine Voodoo II.
If these are legit, I'm tempted to grab a few more for my collection. I've got one working and one dead one now... though I know the dead one just needs a reflow.
Sadly a LOT of voodoo hardware is a bit like the early red ring of death XBox 360's. The hot/cold cycle breaks the surface mount solder joints. Behaves like you've got bad RAM when if you flex the board slightly the problem clears up. Two minutes at 150F in the oven or gently wave a heat gun over the RAM and it's good for another couple months.
Did that one too many times to my own Banshee, it's dead now.