Terrible Performance on 6950s

[notaek]

So yesterday my 6950's were running at 450-500khs each (unlocked).  For some reason my computer shut down, not sure if this is related, and when I turned it back on my cards started only getting 300khs.  I have uninstalled 13.1 catalyst and 2.8 SDK and reinstalled it, and I still get 300khs.  My 7970's still run at full 740khs and seem to be unaffected by this. 

I do know that using catalyst 13.4 got me around the same speed I am currecntly getting on my 6950s, but I am had been running these cards perfectly fine on 13.1 until yesterday.

Any help would be great.

[suryc]

Maybe this is too simple, but do you have dummy plugs in the 6950s? I had a similar problem that hash rates would drop for no apparent reason and it was solved by using the dummy plugs (or plug all of the cards into a KVM or Monitor).

http://www.overclock.net/t/384733/the-30-second-dummy-plug

[notaek]

Maybe this is too simple, but do you have dummy plugs in the 6950s? I had a similar problem that hash rates would drop for no apparent reason and it was solved by using the dummy plugs (or plug all of the cards into a KVM or Monitor).

http://www.overclock.net/t/384733/the-30-second-dummy-plug

Hmm I wouldn't dismiss the idea of needing dummy plugs if these cards hadn't been getting up to 500khs for months until yesterday.

That is where most of my confusion stems from.

[notaek]

Still haven't fixed it.  Not sure if I should try different drivers.

[computerparts]

What are the temps? Could be throttling.

[notaek]

They get to 70 degrees C at their maximum.  One of them usually hangs out at low 60's.  I have two of them by the way.