Recently 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 het, thanks to AMD's new Dual-BIOS feature if something would go wrong, you can switch back. 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. Your graphics card needs to be a reference design sample.
Radeon HD 6950 to HD 6970 Flashing Tools download from Guru3D.com