Turns out they did put Phenom technology in the cards! Have fun people!
Unlocking the additional shaders is done by flashing the card with a HD 6970 BIOS. You can find a few in our VGA BIOS collection. Any of these BIOSes will work on any reference design HD 6950 card. You could use the ASUS BIOS which comes with higher clocks & Overdrive limits and enables voltage changes via SmartDoctor, or stick with one of the reference BIOSes in case you are afraid the clocks might be too high.
I will describe the method for flashing from within Windows, which is safe enough on these cards because of the dual BIOS feature that enables easy recovery.
1. Grab ATI Winflash from here (32 & 64-bit).
2. Download HD 6970 BIOS. The Sapphire one I linked to will work on all reference design cards from any vendor.
3. Make sure the BIOS switch on the card is set to the 1 position (pictured further down if you don't know where it is).
4. Run ATI Winflash, click Save to save your BIOS, so you have a backup in case something goes wrong.
5. Load the HD 6970 BIOS into Winflash by clicking Load Image, followed by Program.
6. Let the flashing process complete and reboot your system.
7. Check the shader count using GPU-Z, it should show 1536. Make sure you use version 0.5.0 or newer, the official 0.4.9 version does not support HD 6900 Series properly. If you see a shader count of 1600, your GPU-Z version is outdated.
8. To ensure maximized performance open Catalyst Control Center, go to the Overdrive tab and set the PowerTune slider to the +20% setting. The "Testing" section of this article has more data on that.
9. Check stability in Windows desktop applications and games.