Almost correct,
All Voodoo II Chips are made by 3DFX, but the actual boards are put out by the various companys like Diamond, Creative, ect. (Although I hear that most of THESE boards are actually mfg. by one or two nameless Companys in Taiwan). Anyway.....
You CAN use two boards together from diff. mfg's as long as they are "referance design boards" and use 3DFX referance drivers.
Referance means the design of the board is a copy of what 3DFX designed to be the optimal layout (In their opinion) of where all the components go on the board. Some companys like Canopus choose to go their own route and make a improved board that would be then called a "non-referance board" and because of the differant layout they will not work together. Hows that?
Good luck,Steve.