There was actually not much need of drivers or firmware. 3Dfx products had a very simple and straight forward way to write commands directly to registers [1][2][3].

1.: https://web.archive.org/web/20180220234020/https://www.openg...

2.: https://web.archive.org/web/20180629191415/http://www.opengl...

3.: https://web.archive.org/web/20180628125330/http://www.opengl...