Random Stuttering and Black Screens - Weirdly Low FPS in Games

[Logan Primus]

This post is going to be quite nebulous as any test I know to carry out has done nothing to shed any light on my issue.

 

I will list the games I am having the issue in along with the issues I've been having;

 

League of Legends - Random FPS Drops to around the 20s, Microstutters and full on Black Screening for about 4 seconds with sounds still playing but I can't interact in any way with the KB&M.

Ghost Recon Wildlands - Literally regardless of settings Low all the way to Ultra I get probably 4 to 9 FPS at all times, not getting any better or worse with prolonged running and all graphical elements take 5 minutes to slowly pop in.

Skyrim Special Edition with Realistic ENB and around 50, mostly texture, mods runs at about 30 FPS (or lower) - I removed the ENB and created a bashed patch and also lowered in game settings and still get the same 20-40 FPS.

All 3D games (except minecraft and Skyrim) - random geometry stretching (such as a part of the ground will be stretched into the sky), random GUI elements not showing correctly

 

I overall feel like my FPS performance is awful for a relative good PC based on the games I'm trying to play, it's not that the FPS is low it's the rapid changes in FPS that get to me the most because it's noticable and can last for 30 seconds to a minute each time it starts.

 

Herein lies the problem, I have NO idea what is causing it (I'm not even sure it's a GPU issue, but it seems the most obvious) and I have no idea how to *know* if it my GPU and not another thing causing weird issues like Paging Issues maybe??? 

 

I ran a long HDD scan on all my drives (I run most of my games off of my 1TB HDD except for LoL) and my drives are all super healthy according to the test results, I ran the memory scan that windows has built in and got nothing back. That leaves GPU or CPU, but this is where my knowledge on Troubleshooting ends and my question begins;

 

Is there any way I can know for a fact what is causing these issues without wasting a bunch of money I don't have replacing parts?

 

Here are my PC Specs;

Windows 10 Pro 64-bit

Intel Core i7 6700 (bought "as-new" from eBay)

16GB vengence LPX DDR4 ((I Think 2666Mhz) (bought new))

Sapphire NITRO+ Radeon RX 580 8GB GDDR5