Question GPU Usage dropping slowly while playing, causing stuttering

[CrazySpelz]

Hey guys,
I hope someone can help me with this.. having problems for a while now, but only with 2 specific games. (Weird thing is, these games dont have high requirements for PCs)

So first encounter with this problem was the Mass Effect 1 Remaster, while playing my GPU Usage dropped from 99-100% (perfect Framerates) to 20% and less. (10-15 FPS at worst case) and stayed low forever until I restarted the game. Found no solution back then, si I played the game and restarted every hour.
Now Im playing Bioshock Infinite Remastered, and I got the same annoying problem. Btw, I didnt have problems with Bioshock 1 and 2 Remastered.
I checked the temperatures, everything is okay, GPU goes to 80C° maximum. CPU Cram and Ram are fine too, and stay between 30 and 40% all the time, while playing. No changes here, its only the GPU.
Newer Games, that have much higher requirements for the PC work perfectly. For example AC: Valhalla or even Red Dead Redemption 2 on high settings. Played hours without any problems. Its only "older" games, that cause this problem. I tried to reinstall, reinstall graphic drivers completely new. Tried "stutter" fixes for Bioshock Infinite (setting VRAM higher in the Game Config file, deactivate VSync etc), nothing helps. I dont think its my Power supply either because then I would have much more problem in the heavy new games, that put all my PC to 100%m but they work perfect.

I play with an I7 7700k (not overclocked) and an RTX 2070 Super.

Please someone help me, because this is getting really really annoying.

 

[rgd1101]

What the cpu/gpu temp and usage during the game?
brand and model of the psu?

 

[Maestro Colby]

That’s the thing about older games, they weren’t meant to be paired with 12gb graphics cards.

 

[CrazySpelz]

Oh, PS: Game works perfect about 1 hour on 99% GPU Usage. Then the drops begin, and after another hour Im at 50%. Then the game gets unplayable with audio glitches and stuttering. And like I said, no temperature problem.

 

[CrazySpelz]

What the cpu/gpu temp and usage during the game?
brand and model of the psu?

Temp GPU is about 75-80C.
Temp CPU is about 70C.

But even if it was a temperature problem, why are games that take everything out of my PC working perfectly for 8 hours+ and games from 2010 are overheating it. That would make no sense at all.

Actually, I dont know about the psu. I only know, that its 500W or more and I had a long talk to a computer specialist about my setup and what I need, so it should be okay.
But if its important and you want me to, I can turn out my pc and have a quick look at it and tell you exactly what I have^^

PS: When I start playing I have 200 FPS, how is that possible. I have VSync Ingame turned off, but still using VSync in my Nvidia control panel so NVIDIA settings should cap my FPS at 144? Somehow it doesnt work.