1. The GPU needs the work done and the cover off to the case.
It's similar to this article:
2. There's a memory leak in the OS or driver.
If a reboot cures it for same hours, it's 99% sure it's a leak. Nothing you can fix but to report it. Or switch to Nvidia and hope it's better.
Finally there's that mouse. Try it sans drivers.
Hello, when I play game's like CS:GO(Counter Strike: Global Offensive) I tend to get massive FPS lag whenever I move my mouse left and right(might be anywhere but left&right are the worst spots).
I just recently wiped out my computer 2 days ago because of the issue. I had Windows 7 now I'm on Windows 8.1. When I first turn on my computer and play it doesn't get fps drops. It's only after 5-6 hour or so of it being on from what I've seen. A restart fixes it but I can't tell when it's going to happen and in competitive games you can't quit or you get a temporary ban.
Graphics Hardware: AMD Radeon HD 6900 Series
Processor: AMD FX(tm)-4100 Quad-Core Processor
Operating System: Windows 8.1 64-bit
Ram: 16 GB
Mouse: CM Storm Spawn (Gaming Mouse)
Polling Rate: 500
If you can help please try.