Perfomance and stutter issues

[SoM3]

My PC - Nvidia GTX 760 2GB, 8GB ram, AMD FX 4170 quad core
The game have awful stutter, every 1 second game skips a frame or two to the point of being unplayable. Turning off the refresh limit doesnt help, what did help was using the msconfig to select 2 cores at boot. But that made PC use only 2 cores, which makes perfomance much worse. Is there is a way that i can play with 4 cores without stutter?

[Maladiq]

It might be because of the Steam DRM? The Witcher 2 had horrible performance issues because of it.

[foobar]

Have you installed the latest BIOS to avoid the microcode bug in the FX CPU?

Otherwise: Read the thread "READ THIS BEFORE POSTING" and come back with the diagnostic files.

[SoM3]

Witche 2 works fluently. Also, no, but no stutter in other games