Can you tell me what CPU, and RAM you are running?
I used a Sempron 145 and a cheap 8GB stick on each rig.@crazyates: do you think that my experiment with 3 PSU (2 for 2 vga each, and 1 for 1 vga and mobo) should be good?
i have only a question about it, can the risers be powered by all the PSU or i must use only 1 psu for 5?
I'm using 3 PSUs on my 290 rig, but a 5x 280 rig may be doable on only 2x 750W PSUs. i have only a question about it, can the risers be powered by all the PSU or i must use only 1 psu for 5?
Either way, I don't think it matters which PSU powers the card, and which powers the risers. I typically put 4 risers on whatever PSU has the least load, and then the 5th riser on the other PSU. I basically do this because our risers take SATA plugs, and our PSU only has 4 SATA plugs per cable.
TL:DR Your GPU doesn't have to have it's PCIe plugs and it's riser powered by the same PSU.