I never got 4x5970s running in Windows 7. Tried optimizing bios (turning off everything not needed), clean install, tried 2 different MB. No dice.
It would BSOD on installing drivers on 1 MB. Trying 6 GPU worked, and mined fine. Adding two GPU worked, rebooted, still good tried to mine and hardlock and/or "AMD display driver stopped responding". On the second motherboard it wouldn't even install windows w/ 8 GPU installed. Got to the point where it reboots for first time and hardlocked BSOD.
I tried countless combinations of drivers versions (w/ SDK runtime seperate), also tried not installing any drivers first and installing all updates & SP and then drivers. Tried preventing it from installing any system drivers to get AMD driver in first and then other drivers. Nothing.
Not saying it is impossible but 8 GPU wouldn't work for me. 7 GPU worked fine though. I grabbed a spare 5870. 3x5970s + 1 x5870 worked but 4x5970s didn't.
I finally got it working in Linux (another long process). I think you mistyped linux is fine for overclocking you just can't overvolt. So likely I am looking at a BIOS flash to raise the core voltage.https://bitcointalk.org/index.php?topic=66606.msg773184;topicseen#new