With 6 7950 cards, you should go with 2 rigs, both wit 3x7950.
For each rig you should get decent PSU, somewhere in 800W range (not less than 750W) with single 12V rail design.
Price difference between 2x 750W PSU and 1x1500W PSU (for 6x7950) is more than enough to buy 1 motherboard, CPU, HDD and 4GB of RAM.
You will avoid any potential windows problems when running 6 GPUs on one system (I didn't see a singe system with more than 5 GPUs), and you will have couple of inches between cards, unlike with 6 cards where you can't get more than 1". Like that you will have better cooling, and quieter system.
Not entirely correct. you could just use 2x 750s for the single six unit. I run six gpus with win7 and no issues. However the spacing is a valid point. to use 6 gpus you have to have a custom case.
thats interesting..
i just got 15 x sapphire r9 290 tri x and was going to do 5 rigs with win 7..now i think ill try 3 rigs with 5 cards..
i already have 3x Gigabyte 990XA-UD3 AMD 990X (Socket AM3+) DDR3 Motherboard and 3x Silverstone SST-ST1200-G Strider Evolution Gold Series - 1200 Watt
could i run 5 cards on this mobo in win 7? how much extra power would i need for each rig? would i run 3 or 4 cards off the 1200w?
could you tell me exactly what else i need to make it work..ie specific power risers, things to connect psu's etc.. (Its my first build- so will need it spelled out)
thanks