Two days ago what we initially expected, it became apparent that the Radeon HD 6950 in fact is a 6970 with shader processor clusters disabled. You'll need to re-flash your card though.
You can perform the flashing process from within Windows and thanks to AMD's new Dual-BIOS feature if something would go wrong, you can switch back.
Unlock your Radeon HD 6950 towards a 6970, Merry Christmas:
More info:
Download package with flash software and BIOS:
We successfully tested an unlock on a HD 6950 cards. Other have tried one AMD engineering sample, one HIS media sample and one ASUS retail card. All of them unlocked perfectly and run at HD 6970 speeds now.