Actually I sort of take that back.
the Mac I eventually installed that in was a clone, a Power Computing machine. It had an ATI Rage II (4MB) onboard. Borderline 3D de-celerator.
But it did have one very important use later in life...
iD Software released the Quake 3 Test to the Mac platform first, citing the consistency of the OS and hardware making it a better platform to begin public testing on. Suddenly PC gaming sites were rushing to the stores to pick up iMacs so they could play the game and write up articles. (which is the story behind this Penny Arcade comic)
http://www.penny-arcade.com/comic/1999/04/28
By then I had the Techworks Voodoo1 card, but proper OpenGL drivers hadn't been written for it yet. There was a hobbyist working on a Mesa GL wrapper for Mac in his sparetime; and suddenly it became his responsibility to make Quake 3 work on non-ATI Mac graphics cards. While he was working on that, I managed to get Quake 3 test to run on mine by disabling the Voodoo card. Had to run it in the lowest settings and resolution, but it worked and was playable (about 10-15 fps or so).
Later he released a new Mesa GL that worked with Quake 3 Test. Night and day difference it made. Buttery smooth 30 fps and high detail settings.