HD 6950 overclock problem

[bigdaz84]

I am currently trying to o/c my 2gb Sapphire HD 6950 using Sapphire Trixx and benching with Furmark.

For furmark I'm doing a 1920x1080 5 minute bench with 4xaa on.

I can get gains from increasing the memory clock from stock 1250 mhz to 1350mhz. The score goes from 2800 to 3400. A good 20% increase. When I then move onto increasing the clock speed my score gradually goes down the higher I move it.

I have the power slider at +20% and have tried slight increases in the voltage. Temps are fine at 62 degrees.
GPU-Z shows no dip in clock speed. GPU core is at 95% for all tests.

Any ideas guys please? Thank you.

[bigdaz84]

20% increase was due to extra memory speed making a difference with the aa. With slight voltage increase and memory at 1325Mhz I started to see increases in performance with increases in clock speed. Up to 920 where it all went a bit wrong.