i had some experience with those switches and some old mobos for a couple of last weeks. neither g31 and g41, nor h61 and some too old chipset mobos didn't see any cards through it, but h81 works well. i don't have any amd mobo, but due to their specs it should work too. well, getting a cheap 2-pcie slot h81 mobo to build a 6 gpu rig looks like a good plan now.