Hi - I think i have bad news for Asus P5K Pro motherboard owners. - It will not work.
I tried number of time with Asus P5k P5k motherboard (with latest bios in it) and 2 x Club3D radeon 4550 cards (with latest drivers).
Motherboard support claims that Club3D radeon 4550 card/s are faulty.
But both works fine, in 1 x combination and 2 x combination but i cant activate in CCC Crossfire option, i cant see it.
I tried, with
1 card on PCI-E 16x slot = works fine
1 card on PCI-E 4x slot = works fine
2 cards on PCI-E 16x and 4x slot = works normally, but not crossfire available
Club3D cards are crossfire cards
Asus P5k Pro is "crossfire" compatible only on manual and webpage, not realworld.