I'm not sure if this has been discovered yet. I think it is very exciting, and very important for anyone with an AMD (ATI) GPU who wants hardware MPE acceleration.
It is possible to use Hardware MPE acceleration while using an ATI video card as your primary adapter, and a lesser CUDA Nvidia GPU as a secondary adapter not connected to any monitor.
RAM: 8 1333
GPU2: GTS 450
As you can see, I have a Nvidia and AMD GPU in the same system. The 5870 is obviously by far the most powerful of the two, and it is what I use to record rendered footage using FRAPS.
Recently, I became aware of the powers of hardware MPE. I concluded that the best way to obtain HMPE and maintain my FRAPS recording was to purchase a GTX 480. However, this was out of my wallets league as I could not sell the 5870.
I was already aware that PhysX (A CUDA physics calculation library) could only be run on Nvidia CUDA GPUs (Like HMPE). Many Nvidia card users used secondary CUDA cards to accelerate physics calculation in games. ATI card users could not use a secondary Nvidia card for physics calculation as the Nvidia driver locked down PhysX in the presence of an active ATI GPU. Luckily a clever fellow called GenL managed to hack the Nvidia drivers to force PhysX to work in the presence of an ATI GPU.
I hypothesised that if I performed that hack, HMPE would gain access to CUDA in a similar fashion to PhysX, thus allowing me to buy a far cheaper GTS 450 and pair it as an HMPE renderer with my 5870. After buying a GTS 450, I failed at implementing the hack and was about to give up.
HMPE worked when my monitor was connected to the GTS 450, but if i tried to start PPro with the 5870 connected to any monitor HMPE was unavailable.
I had two monitors connected to my GTS 450, and was playing around with adding stupid amounts of HMPE accelerated effects to an AVCHD clip. Realising that it was impractical to constantly switch the DVI cable from 5870 to GTS 450 I decided to leave my primary monitor connected to the 5870 and give up on HMPE. So, I reached around behind my computer and did it, but crucially did not quit PPro before I did so.
When the screen flickered back to life, the yellow HMPE preview bar was still yellow. The timeline still scrubbed perfectly smoothly. HMPE was still working with a 5870 as the primary monitor: The PPro window was on the 5870 monitor, and the 5870 was rendering the window!
I found that provided I did not close PPro, I could switch between HMPE and SMPE at will, all while using the 5870 as the primary adapter.
I tested this using a 10 second composition of 3 AVCHD 1920x1080 Clips with CC, drop shadow, gaussian blur, edge feather, Basic 3D, transform, Ultra Key, drop shadow applied, rotatating amongst each other. I could still switch even if the 5870 was the only card connected to a monitor.
Rendering this test clip via PPro direct export takes 30 seconds in HMPE mode with the 5870 and 1.43 in SMPE mode with the 5870.
However: Rendering performance in AME stays the same whether I selected HMPE or SMPE. I believe this is because AME is a separate application that 're-detects' the ATI card and disables HMPE before beginning the encode, in the same manner that restarting PPro while using the 5870 removes the HMPE option. Rendering the clip in SMPE and HMPE modes using the GTS 450 gave the same 30 second vs 1.43 minute result.
Therefore, as long as you are happy to encode via direct PPro export you will still see the benefit of HMPE while using an AMD card as the primary adapter.
I hope this is as terribly excited to other users of ATI cards as it was for me. This has saved me several hundred dollars.