You are correct in that multi-threading is only available on OSX. That's because of the system only recognizing it in OSX, and then C3 (or, C2 for that matter,) can access it as well. I use OSX on my home machine, a dual 1Gig machine, and it is the balls! Everything is done in half the time! Yeah! When you are doing a render, if you've noticed the yellow box that shows where it's rendering, it becomes a yellow box with a '1' on it, and a 2nd red box with a '2' also appears and they both swap off areas of the render. It works. It works well. Try it, you'll like it. ;>