One thing that may of been missed by a lot of folks in the release of Premiere Pro CS6 - support for real time full res full frame effects by using OpenCL in Mercury Playback Engine. Almost everything thats done with CUDA on nVidia cards is also now being done as well in OpenCL on ATI / AMD GPU's. Read more on adobe site for the details. So I wanted to try this out on my iMac 27" as I figure it had a new enough GPU and enough VRAM to work.
A Little Hacking To Get Your GPU To Work
The list of offically supported GPU's is short - just 2. However its pretty easy to get your own GPU to work provided it meets the major requirement ( at least for CUDA ) of at least 768mb of VRAM. The GPU in my 2010 iMac is a 5750 with 1G of VRAM. A slightly older GPU, but enough VRAM to give it a go. Here is how I did it.
Pre Update, 10.7.4 is highly recommended as it has major OpenCL improvements, so I'd do this update first.
1. Locate the actual Premiere Pro application
2. Right click on the Prem Pro icon and in the contextual menu select "Open Package Contents"
3. Open up the Contents folder
4. Right click on the file named opencl_supported_cards.txt and do Get Info on the file
5. At the bottom of the Get Info window click the lock icon, enter your admin password when asked
6. If Sharing and Permissions isn't spun down, do so. Change admin at least to Read & Write, I also changed everyone as well. This will allow you to write the file back after changes
7. Change to Read & Write
8. Close the Get Info window
9. Now open the opencl_supported_cards.txt file into TextEdit. You'll see 2 cards list there.
10. Go to the OS X's top left apple button menu and select About This Mac
11. In About This Mac hit the More Info Button.
12. On the first screen ( Overview ) you'll see your GPU model. Drag the mouse cursor over the text so it selects, then hit Command C ( copy )
13. Back to text edit, go to the end of the last line. Hit enter, then paste the name of the GPU in.
14. Hit Save and then close the file
15. Start Up Prem Pro and enjoy hardware MPE on your ATI / AMD GPU
What If It Doesn't Work ?
If you start up Prem Pro and it crashes, you need to go back into the opencl_supported_cards.txt and remove your GPU. If you find, with hardware MPE enabled that you are not stable, quit Prem Pro and remove the listing. So far my 5750 works fine, of course YMMV, I'm not responsible for you trashing Prem Pro, ect. Do this at your own risk... and have fun seeing if your GPU works !