Yes, they are USWC compatible. All modern cards, well, just about everything that came out after 1997, are USWC compatible. A lot of S3 cards are not, like the Trio 3D, and crap like that, but I doubt that you would have one....hehehe.
All Riva cards after and including the Riva128 are compatible, I know the entire line of Matrox Gxxx are; 3dfx implements it in their own drivers rather than needing to go through the BIOS.