Experimental tweak. Back then, everyone was wondering if it does anything.
Im not sure, but maybe it is helping. But still, remember, this game is very single threaded, so you need strong Cpu with big single-thread performance. You can also try to experiment with Threaded-Optimalization in Nvidia Control Panel.
How to use: If you have 6 cores processor, write 5, because first value is 0. So with 8 cores Cpu write 7. Its always -1 of cpu cores.
Instalation: Unzip and place file to root or config folder of the game and change value, as described above