Hey,
Back in the day I had a HD 7850 and got in CS:GO like way over 120 FPS. Today I built in my GTX 960 and everything works but the game performance is complete shit. I get in CS:GO on everything min @ 720p 80 FPS max. The CPU (Phenom X4 @ 3,1 Ghz) is bored on 50% and the RAM (4 GB) is on like 600 MB and not even close to be full.
Something is definitely wrong. I checked the 3D settings and disabled the energy saving mode already, I disabled Shadowplay and the Nvidia streaming service. It's gotta be something software related because the 7850 obviously worked flawlessy.
Help?