Apple has posted the final list of GPUs compatible with OpenCL in Snow Leopard. However, there are several conspicuously missing from the list, and some other users were surprised to find certain cards missing, apparently not quite clear on what makes a card compatible. The short answer on what makes a card compatible is "Unified shaders". This thread isn't really for going into great detail about them, so I'm just going to send the curious over to Wikipedia to study up on GPGPU. If you have a compatible card, you can use OpenCL with it. If it's not compatible, you can't. The system it is installed in does not make any difference. Note that even if you do not have an OCL compatible card, you can still run OpenCL enabled apps, as your CPU is itself an OpenCL device (OpenCL was designed to work this way). You will simply not be able to offload that work to your GPU. To recap, these cards are all officially compatible according to Apple: Nvidia: -8600M GT -8800 GS -8800 GT -9400M -9600M GT -GT 120 -GT 130 -GTX 285 -Quadro FX 5600 -Quadro FX 4800 ATI -4850 -4870 Inexplicably not on Apple's list. These cards all have unified shaders and were shipped in Macs: ATI -HD2600 -HD2400 Intel -GMA X3100 NOTE: As these cards did not appear on the revised final list, we can only conclude that nobody could be bothered to write an OpenCL driver for them. These are all older, low-performance cards, and as such it was likely judged they would not perform well enough as OpenCL devices to make it worth the time Not on the list either, despite also supporting unified shaders. However, none of these cards were ever actually shipped for Macs. They were all aftermarket add-ons to the Mac Pro. ATI -3870 Confirmed NOT compatible as of 10A421. Could be made compatible with a driver update. This may be present in the final build, but it's unlikely. If an update comes, it will likely be a standalone download from AMD Note 1: The 8800 GTS is listed as compatable with SL. This card came in both G80-based and G92-based (the latter being effectively the 8900GTX renamed to avoid cannibalizing 8800 Ultra sales). Neither ever appeared in a Mac. However, this latter version is very similar in both name and design to the 8800GS in the iMac, which is curiously not listed. There is a good chance this is a typo, and the 8800GS is actually "on the list". Apparently this was the case. The error has now been fixed on the Snow Leopard tech specs page. Note 2: Any card that shipped in a Mac but is not listed anywhere on here lacks unified shaders and is incompatible by default. _____ 8/18/09 - Some compatibility testing is under way in this thread: http://forums.macrumors.com/showthread.php?t=766219 Of note: It appears (need benchmarks to confirm), that as theorized by some, SLI/Crossfire is NOT required to allow multiple cards to be used as OCL devices, and it in fact seems to work fine with multiple totally different cards, such as 9400M+9600M GT or GT 120 + 4870. Again, this is just based on all the cards showing up at once in a list of OCL devices, and we will need benchmark tests with and without the extra cards to know for sure if this works. P.S. - Because somebody is gonna ask again....GeForce Boost (both GPUs at once for Core Image/OpenGL) on the MBP is still meaningless due to the usual issues with card scaling in heterogeneous SLI, and thus is STILL not supported in hardware. _____ Official list revised for Snow Leopard launch, thread has been updated to reflect that.