PCIXE16_2 (black slot) and PCIXE16_3 (blue slot)
It is impossible,Cards are in contact :(
(The crossfire uses the 2 blue slots x16, no ?)
PS: why this hack sli work on rampage extrem(x48), on 2 slots blue x16, with bridge sli, 2x MSI N285 GTX Super Pipe OC (The same) windows 7 64 bit...