I have 2 6950s one unlocked to 6970 and one not unlocked. Both are running at ~ 900 MHz and are within 3% of each other performance wise so there is not much difference.
thanks guys, i have a feeling 6950 is the way to go.
dinzy, are you saying 6950 and 6970 dont have much performance difference in term of bitcoin mining?
Yes. It looks like the shaders do not give you anywhere near as much boost as clockrate. The 6970 will guarantee you 880 MHz but most 6950s should hit that. That being said, some cards are unlockable so it would be better to get those since you would probably have 10-15 MH/s more per card. 3 of those will add up so that is an important consideration.
My unlocked one is a MSI twin Frozr II and it is certainly unlocked and not throttling. It throttles when I go over 900 MHz.
The locked one is an HSI one from newegg, the cheapest one for 2GB. The unlock flash "works" but does not do anything. I think they just shorted a line to ground so you cannot actually write to the BIOS. My guess is that all cards are unlockable, but the most recent ones have flashing disabled.
Do you live near a Fry's? They have a generous return policy and typically have an older stock. You could probably buy 3 of the twin Frozr II OC editions and unlock them to 6970 shaders and overclock to ~ 900 MHz