MB: P8P67M Pro
GPU: Asus 6950 1GB
Factory bios, no overclocking
SSD, 6gb ram.
When I run any miner (hashkill, phoenix, diablominer), or any combination of miners, I either get around 50-75% utilization of both cards, OR, I get 99% utilization of one card.
Basically, I either get sub-optimal performance from both cards, or I get expected performance from one card while the other is entirely starved. This happens at random. If I do get a stable 75%/75% from both cards, it will eventually (maybe after hours) turn into either 99%/0% or 0%/99%.
I am running 64-bit ubuntu, 11.04 and Stream SDK 2.4. The two PCIe slots the cards are connected to has x8 speeds according to the motherboard manual. I have installed one crossfire bridge (otherwise I can't use the 2nd card in linux). The temperatures are fine. My CPU utilization is almost nothing. Both cards easily do more than 300MH by themselves. I do not understand where the bottleneck is.
Any help with this would be highly appreciated. I'll gladly give 0.1-1btc tips to information that makes a difference.