Fps drops and CPU usage drops

[Caaruw]

So I have had this problem for a year or so and I seem to have tried everything. The problem is that I am getting a huge FPS drop (from 300ish to 35 fps) for 1-2 seconds and then its fine. I have been keeping an eye on the hardware monitor meanwhile playing and I do see a drop in CPU usage when theese FPS drops occure. The drops happens while playing any game such as League of Legends and World of warcraft and it doesnt show any significant pattern. It just happens randomly.

Setup:
ASUS Maximus VII Hero
Intel Core i7-4770K
Asus Geforce GTX970
Samsung SSD 840 EVO 250GB
Dual monitors
8Gb RAM
etc

What I have checked and tried:
CPU and GPU temperatures are fine
Checked all drivers and they are up to date
Changed power saving settings in bios and windows,
Formated the whole PC
Switched operating system (from win 7 to win 10)
Bought new PSU and Motherboard,
Switched PSU cable
Removed dust and crap from PC
Updated bios

What else can I do? Feels like the only thing I havent tried yet is buying a new CPU but I really dont wanna spend that kind of money if it wont make a change..

 

[Gingerbread]

Try forcing it to run always at max clock speed so that it doesn't underclock. Also are you sure it doesn't auto underclock due to high temps? I know you said it doesn't but when the usage drops the temp will drop as well.

 

[Caaruw]

I am sure. The temp is never over 60, just bought a new cooler. I have it clocked to max which is 4,6k. Although i think the problem might be solved. I dont wanna jinx it but i re-installed some features .net framework and Microsoft visual C++, and havent had any lags since. Of course it gets fixed the minute I upload this here xD

 

[NightAntilli]

I suspect that dual monitors + 3.5 GB of the GTX 970 = trouble.

Download and open GPU-Z, monitor the RAM usage and GPU load of your graphics card.

 

[Austin Johnston]

Normally I would say that sounds like a GPU memory issue, lower your textures, but that doesn't make sense for LoL. Something you may want to try is unparking your cores. Do 1 or 2 cores go to 100% while the others stay relatively low load?