I was wondering how does FSAA actualy work in multi-GPU setups from 3dfx?
I know 3dfx used supersampling (rotated grid if I'm not mistaken), and it is fayrly easy to imagine how 3dfx FSAA works for sigle chip configurations, like VSA-100 2x mode (Voodoo4). My question is how FSAA works for multichip setups into those modes:
-Voodoo5 5500 : FSAA 2x
-Voodoo5 6000 : FSAA 2x and 4x
I can imagine for example 2 possible solutions for the FSAA 2x when Voodoo 5 5500 dual gpu is used, it is up to you to point it out the right one:
-Only 1 chip does FSAA 2x, the same way it works for Voodoo4; the other chip doesn't do FSAA
or:
-FSAA 2x is composed by supersampling 1 image procesed by the first chip with 1 image procesed by the second chip, so the result is FSAA 2x
The last hyphothesys doesn't explain how 4-way SLI does FSAA 2x though...
I admit I am yet a novice, but I want to learn more  

I dont think so,that would be inefficient.my bet would be:

-voodoo5 5500 2xFSAA: one chip rendering each scene one time,resulting in 2x FSAA
-voodoo5 5500 4xFSAA: one chip rendering each scene two times,resulting in 4xFSAA

-voodoo5 6000 2xFSAA: a pair of chips rendering each scene one time,resulting in 2x FSAA
-voodoo5 6000 4xFSAA: one chip rendering each scene one time,resulting in 4x FSAA
-voodoo5 6000 8xFSAA: one chip rendering each scene two times,resulting in 8x FSAA

that would be more logical.I think.

ah Thanx Gamma742 just what I needed

Both chips render the same frames, then they're combined. That's what you see on your screen.