I have 6 cards per rig, 3 of them on powered risers... two rigs... 3 Seasonic 1250 Watt gold power supplies. Each power supply powers 4 cards.
I have the Gigabyte 990FXA-UD5 and the MSI 990FXA-GD80 and they both can handle 6 GPU's I believe (still waiting on 1x risers to arrive). It looked like they had been out for awhile so I didnt know if there was anything better on the market that most people were using or not.
Hey I have the GA-990FXA-UD5 and do you have to short one of the slots to get the 6th working?
I'm curious what kind of luck you have had getting six cards to run on this mobo. I have two of these going each with five cards. Four of the cards are on the 16x PCIe slots and one is on a 1x PCIe slot. When I built the rigs I couldn't get the second 1x PCIe to work. Just curious if you had luck maxing out the PCIe's on the GA-990FXA-UD5.
(My friend was surprised I got Gigabyte motherboards to work at all! They don't always reboot correctly on the first try--could be the cheap SSD or anything else though--I'm no expert!)