Hi,

Sorry - I forgot all about giving the PSU info - THE most important bit !

In short, no, Ive found you cant run 3 cards on a 1250w PSU - at least not on my XFX 1250w gold - its runs for a bit, then just powers off...    I dont even think you could run them on a crazy money 1600w+ PSU as im pulling 1700w...

So I have a 1000W gold, which is hooked up to the mobo and 2 of the 7990 cards, and the 3rd 7990 card is hooked up to a spare 600w psu I had lying around.   I "jumped" pin 16 of the connector to pin 17 (ground) to get the second PSU to turn on.

Im going to add a 4th card when I get a chance for fun...

Lowering the card voltage / clocks didnt lower the draw at the wall hardly at all.

I got the cards from an online retailer in the UK who managed to get a big stock - all sold out in a day or 2 though...

I did find that putting the thread concurrency up over 16000 made the box run out of ram and crash windows - and I dont get any performance gain over 16000.