ProcessAffinityMask

[maclean525]

Affinity Mask works like this:

Each core is one bit of an 8 bit byte. So if you have 8 cores:
11111111

Here's how you calculate those affinity mask numbers:
128 64 32 16 8 4 2 1

So if you wanted the game to use only the first two cores you would set it to 1+2=3. If you wanted it to use all 4 cores on a quad core machine it would be 1+2+4+8=15.

From my experience with other games, hyperthreading on a quad-core is counter-productive so turn it off. In addition freeing up the first core for windows seems to reduce micro-stutters (in other games I'm talking about here like FSX)

I've found 14 to be the sweet spot for my system (using cores 2,3,4 core 1 free for windows)