That method won't work on many non-reference cards, and unfortunately can cause problems with memory I've heard. But while I followed the thread it has linked in response to it, I learned how to unlock the shaders in a much safer manner.
I should probably write this up in completely in my own directions and get it stickied, as I know a lot of people are going to be asking for this. Anyways, this is a copy paste out of another thread:
1st, you'll want to save a copy of your existing bios. You can follow the bios flash guide steps 1, 3 and 4 to save your bios. This is just in case something doesn't work right (not all 6950 GPU's have fully functional shaders). The flash instructions are here: http://www.techpowerup.com/articles/overclocking/vidcard/159
Just do steps 1, 3 and 4.
Next, download this: www.techpowerup.com/wizzard/Mod_BIOS_HD_6950.zip
(I found this on page 16 of this thread. W1zzard made it, the one who created the flash guide: http://www.techpowerup.com/forums/showthread.php?t=137136&page=16)
Extract the script and copy over the original saved bios into the folder for this script. It needs to be named "original.bin"
Now run the script (it will tell you instructions) and follow the original flash instructions with the modified bios. ( http://www.techpowerup.com/articles/overclocking/vidcard/159
) follow steps 5 through 9 with the modified bios created with the script ( modded.bin )