Bottleneck? i7 start stuck @100% on 1 thread (WIN 10 up 10586.36)

[Nick 5]

Hi guys, hope someone can solve this nonsense.
A few weeks ago my PC started stuttering and dropping frames in every game, even at low details. Rebooting the PC the problem is gone.
So I found out that the first core thread was stuck on 100% at startup (just the first) and that's the cause of the fps drop.
Here's the image:

And this is after reboot, when it works fine:

The system temperature is about 35°C

I have read about energy saving C-STATE in bios, it's on "auto". Can that be part of the cause?

I trust in you!

 

[Deleted member 1560910]

so what is the issue?

 

[Nick 5]

so what is the issue?

"stuttering and frames drop in every game, even at low details".

As soon as it power up CPU (1st thread) is used 100% causing that problem: first image first up left square.
No process requires that permanent 100%, that's the problem.

 

[RobCrezz]

What is the process in task manager thats using up all of that core?