Question Bottleneck or another problem

[Nanosnaker]

Hello there.

Recently I started having problems with my PC stuttering and having lag while watching videos, playing games or starting/closing applications, all this started after I removed the GPU to change the thermal paste on it. Every time the stuttering is happening my CPU is going to 100% usage and then dropping back to 1% usage (I checked for other processes that can use it and nothing else than the process i'm focused on) while the GPU is not used at all. The lag is happening whenever I watch a video in 1080p 60fps or if I play something resource demanding, and the CPU usage is constantly 100% while the video card is only 56%, tho in game fps is not dropping when the lag is happening. I also checked the temps on both and they are normal CPU is 65c when used and GPU is 40c.

Is this stuttering/lag happening because the CPU might bottleneck the video card or something happened with my video card and is now faulty or is something else I can't identify?

PC Spec:
GPU: Nvidia GTX 970
CPU: Intel Core 2 Quad Q9550
RAM: 4x2GB DDR2
SSD: KINGSTON A400 120GB, SATA3
Motherboard: Fujitsu Siemens D2581-A1

Thanks for your help.

 

[Lutfij]

I still have a Q9550 on an Asus Rampage Extreme(X48). You might want to see if uninstalling and reinstalling the GPU drivers changes the issue but I'm curious, You should be a latter gen CPU when pairing it with the GTX970. You forgot to mention the make and model of the PSU as well as it's age.