dual 6950 rig having OC issues - downclocks when

[dinzy]

I have an annoying problem.  I have an HIS 6950 not unlocked that has a dummy plug connected to it and an unlocked MSI 6950 that only can handle a slight OC.

I can run the HIS at ~ 900mHz but it drops it's OC when I shut off the display hooked up to the other card going back to 800 Mhz and loosing a solid 35 MHa.  I am OCing both cards with MSI Afterburner and the program still shows the setting as 899 but the GPU speed on the graph is only 800.   Driver is 11.6, OS is Win7 x64 using the latest GUI miner.

Any ideas?