I'm not sure what's wrong with my setup. I've got an early '11 MBP 15" with HD6750, 2.3GHz, and 8GB RAM. I installed Catalyst drivers 11.12 on top of bootcamp drivers.
I have almost nothing installed but diagnostic apps (in Win 7 boot camp), but I'm having extreme difficulty getting any meaningful OC or undervolt.
With ATT I tried for (what I thought should have been) a modest 750/900 @ 0.955V, but this black screened. I tried that same clock arrangement at the full 1V that's stock, and that didn't black screen right away, but did about 2 seconds into a run of 3dMark06. I haven't done any real fine tuning, but about the best I can seem to do at or under 1V is 720/875.
Undervolting doesn't work at all either - I tried the recommended 600/800@.855V and that was an immediate bust, as was 600/800@0.9V.
Some other wierd behavior - it seems that when I reapply my stock clock settings, they only "hold" for a little while, reverting back to whatever OC actually took previously after about 3-4 mins. Also, I'm getting a LOT of spikes to the full clock speed, as opposed to the 2D clock speeds of 100/150 like it should stay at. All this even though I'm doing nothing but browsing this forum with no other program open.
Do I have a defective card or something? I just bought this thing and I'm beginning to get a bit of a sour taste.