So, need to get this out there but I don't have compete knowledge yet. There is a growing body of evidence that new spin off variant of GK110 chip is having issues with 10.9 and OpenCl. This is from a guy who JUST had me do first GK110B EFI. The GK110B is supposed to be 780Ti but Nvidia is using it in Titan and regular 780 as well. There is a thread at Netkas but it was Hackintoshers and it is tough to tell when their problems are the faking of EFI issues or consistent with Mac Pro. "Celedral" brought me a 780 to mod last weekend and card seemed fine during testing but I just stressed with OpenGl. He has been trying to use it in new RCX that allows processing Red 4K files using GPU instead of CPU. Here is what he wrote me: ...was running RCX (latest beta) and it crashes every time I click on "system" in the preferences. tried it on previous builds as well with no luck I'm running 10.9 Maybe you might have a solution for this? I couldn't find much info on reducer, but people claim it's working 100% with a titan and 10.9. And in another thread here: I'll be testing that GTX 780 SC (GK110B) later tonight with OpenCL. I got this card specifically to edit r3d footage, but having no OpenCL on RC-X is such a bummer at the moment. I hear people are having issues with preview since it's using OpenCL. I noticed this when i previewed a video and it comes up as a incompatible file with 0kb. I don't know enough to actually use the program but I was able to open up and find that System panel. Shows a regular 780 getting there just fine. I will be offering to temporarily trade him so that I can have a "b" card for further testing. Anyhow, anyone getting a PC Titan or 780 that shows as "b" in ROM or GPU-Z is welcome to see if their OpenCl is working in 10.9 and post here.