Here is video from my friend when he plays my game

https://drive.google.com/file/d/1VCTvwrF...ET7Bv/view

The problem is whatever graphic setting is, from maximum to minimum, the game's FPS always at range from 50-60 and drop below 40 when there is heavy calculation like combat, AI process. (I am aware of that it is not because of Vsync)

At lowest setting, He turns off every heavy FPS affection like MultiSampling, FXAA, AO, using 50% render pixels, No shadow, No toneMaping, No bloom etc.. As maximum setting, below 60fps is normal I think, but when changing to lowest, it is all the same. I am sure that D.sync(false) and expect fps goes above 80 or 100 but it is not.

In video, my friend tries to look at the sky where almost nothing is rendered, the direction is pointing to outside of the map too.

My friend's computer spec: https://i.gyazo.com/99cd8f955d6718bd9d0d...6029b9.png

I don't believe that this spec can't handle lowest setting of EE at 60- FPS and Vsync Off What may cause this, while his computer can play Some game like Call of Duty Modern Warfare at good FPS, Team Fortress 2 at 100+ FPS, same as Counter Strike GO.

Edit:
Decreasing resolution to much lower like 800px width can't affect anything too

His gpu might not be the bottle neck, but the cpu might be ?

Thanks for suggestion guys! If it is CPU bottleneck, I will try to cut out part by part of the game to find out which part is killing FPS