Actually, the voodoo3 2000 he's talking about is a reflashed PC voodoo3 PCI card. I have one of these.
What happened is this: before 3dfx made Mac V4 and V5 cards, they offered a beta bios + beta MacOS9 drivers for their Voodoo3 series (afaict they never made a v3 mac card - other companies did some stuff with 3dfx V2 class hardware though). The bios is openfirmware of course. Now, I haven't bothered to try this out yet with my oldworld beige G3 mac (I currently have a MAC Radeon PCI on that machine), but i don't see why it wouldn't work (aside from the tdfx driver never being tested on PPC hardware). If I do I'll be sure to let you know. (By the way: any idea if using this card as a second head with openfirmware bios on PC hardware would work? IIRC, it needs to be softbooted, so it probably relies on x86 bios.) -- Mourad