Only Averaging around 120 fps in CSGO lowest settings with gtx 1060 3gb and i3 8100

Solution
I'd personally check to make sure you don't have v-sync or any other frame limiter turned on, and that your monitor is operating at 144hz. The most logical problem is that you have it set to 120hz (using HDMI) and v-sync is on.


Just because an engine uses multiple cores, doesn't mean they use them all equally. It only takes 1 thread to be slowed down on a single core in order to slow everything down. A single thread doesn't get used on multiple cores, just 1. Although some advanced thread loading techniques do exist these days, they rarely get used and didn't get used back when CSGO was created.

Anyway, it seems like something else is the bottleneck if he's getting 20-30% usage per core.