Not sure if I should post this here or in the motherboard section but here it is.
A friend of mine has a sapphire PC-A9RD580 motherboard which seems to be built for crossfire with ATI cards. He is however considering upgrading to two nvidia 8800 cards in SLI configuration (he's not sure what model yet, although I recommended the GTX's). He has asked me if it will work on his current motherboard (the aforementioned sapphire board) but I told him I'm not sure as it seems to be optimized for ati crossfire. So I turn to you guys to see if anyone knows for sure? Thanks a lot.
Not unless he hacks the drivers for the mobo which will be a pain in the A$$.
SLI and Crossfire mobos work like this:
->ATi crossfire and Intel dual PCI-E boards only support only dual ATi cards. (AFAIK, Intel hasn't released an SLI board)
->NVidia SLI boards only support dual NV cards.
He can, however, use a single GTX on the ATi board.