Quote from: crazyates on March 01, 2014, 05:58:19 PM

So you can run one card at a time, but not both at once? Sounds like a PSU issue.

Crazy!! As much as I don't want it to be a PSU thing... it might actually be?! I need to investigate more, but here is what I discovered (thanks to your prompting). If I put one GPU on each PSU, both will run at gpu-threads 2.

Here are the Watts:

PSU#1 (numbers include LCD)
54w idle with MB, CPU, 2 GPUS on motherboard, but powered via 2nd PSU)
105w while mining at gpu-threads 1 (both GPUs powered by 2nd PSU)
326w while mining at gpu-threads 2 (one GPU on each PSU)

PSU#2
246w while mining at gpu-threads 2 (one GPU)

For the life of me I can't fathom how these brand new 750w Gold PSUs can't handle 2 GPUs who's combine load is under 500w?!
http://www.evga.com/Products/Product.aspx?pn=120-PG-0750-GR

Next I'll start playing with cords and VGA PSU slots to see if there are some magic combinations.