How many processing cores can Unity3D use?

I have the option of getting 3.33 ghz 4 cores processor, a 2.66ghz 6 cores or a 2.93 ghz 6 cores. I know that the middle one will be slower than the last, you don’t have to tell me that. What I would like to know is how many cores can unity use? and what would work better, 4 fast cores or 6 slower ones?

Thanks in advance

It depends.

If you’re talking about playing games, generally speaking, Unity applications are single-threaded. However, there’s nothing to stop you creating your own threads using Mono’s System.Threading - just so long as they don’t directly call into the Unity API. But you could, for example, offload AI calculations to a thread on a separate core. (the functions that are likely to benefit from being in a separate thread are unlikely to directly call into Unity anyway…)

As for creating games in the editor, certain editor functions are multithreaded through an internal job-scheduling system including Mecanim, Shuriken, Multithreaded renderer, Mesh skinning, and Cloth (according to this).