FPS sudden drop after 10 mins

[Jerry_95]

Pc sec:
Cpu 5940X
Gpu 2*Tatian Z 6gb
Storage 512 Gb ssd samsung
A some kind of alienware aio water cooler
Windows 10
Mobo Alienware 0xjkkd
32 gb samsung ssd ddr 4 2133mhz (not yet overclocked)
Monitor Dell s2340m 2k

Not my pc, but has been using for 2 years my friend said.

"Don't know why after 10 min or so, the frame drops to like 40 or so frames,
just have this problem in game but not in normal use, when in game the frames would drop.
for example he runs league of legends from like 800 frame sudden drop to 40 frames and not going up anymore. "

 

[Froberg]

Can you replicate it with furmark or any similar 3D testing tool? http://www.ozone3d.net/benchmarks/fur/
Could be a heat issue, where it'll clock down if it's running too hot, so watch your temperatures.