Based on my rig readings with a 90% efficent PSU.
4x 280x @ 1080/1500 1125mv = 1190W from the wall. 750-755khs per card.
4x 280x @ 1030/1500 1075mv = 1050W from the wall. 715-720khs per card.
4x 280x @ 1000/1500 1037mv= 970W from the wall. 695-705khs per card.
I assume he runs 800khs per card @ around 1160/1800 1120-1125mv. This should pull approximately 1550-1650w from the wall.
Nice post. I'm running on 3 x 280x dual-x now, waiting for the last riser cable. Pulling 929W @ 1080/1500 at 750kh/s per card. At these clocks you say 1125mv. This is undervolted? What are the stock voltages? Is this through cgminer config or done with Trixx?
When I check the three cards, card 1 is @ 1200 VDDC, card 2 @ 1163 VDDC and card 3 @ 1150 VDDC. How can there be a difference with 3 of the same cards?
Also, when I check GPU-Z, card 1 is @ 1.038V VDDC, card 2 is @ 1.013V VDDC and card 3 @ 1.044V VDDC. What explains the difference compared to Trixx?
I did try to undervolt the cards the first day I set it up, while running @ 1080/1500. Tried to undervolt them a little bit down from 1163 and 1150, but the AMD driver would almost instantly crash. Is this normal?
I'm just wondering if it is definitely possible to undervolt while running @ 1080/1500, because I do like the hash rates.