Weird fps drop without actual fps drop.

Pojzon

Commendable
Dec 26, 2016
2
0
1,510
System: Windows 7 64
Motherboard: GA-Z97X-Gaming 3
CPU: i5-4690K
Graphic: GTX 970 (375.95 driver)
RAM: Crucial Ballistix 8GB (2x4GB) DDR3

Hello, I'm having following problem, during playing games my frames randomly drop without actual fps drop - every program that shows fps shows that It's stable, but gameplay feels like 5-10 fps. Now weird part is that in order to fix this I have to open windows task manager with ctrl+shift+end until next random drop.
I believe It's some problem with CPU, but it's not showing any overload in windows task manager, It's not at 100% usage, temperature is fine so I have no idea what could be the reason. Thing I've noticed is that It only happens in window borderless games.
So far I've try:
-Windows reinstall
-Graphic drivers reinstall/try different verison
-Nvidia GeForce Experience uninstall
-Setting power management in windows to max efficiency
Any help will be greatly appreciated. Thanks.