Question PC restarts under load.

[VasjaP]

My pc keeps restarting under heavy load. Im thinking that its a psu issue but im not sure. When i run cpu stress test then it takes about 5 minutes to restart but gpu stress test takes about 10-30 seconds in furmark. When i run OCCT psu stress test then it restarts instantly and that also killed one of my usb ports. I have tried to swap ram and connected bare minimum to try but nothing has helped. I also installed new windows and cleared cmos but that didnt help as well. Temps are fine both cpu and gpu wont go above 65 before restart. Sometimes it also restarts just browsing web or smth but usually only under load. I just want other opinion before i buy new PSU.
Specs are
i7 7700K
GTX 970 strix
16gb ADATA XPG GAMMIX D10 DDR4
PSU: Fractal Design Tesla R2 800w gold rated
Maximus VIII Impact by asus

 

[Koekieezz]

My pc keeps restarting under heavy load. Im thinking that its a psu issue but im not sure. When i run cpu stress test then it takes about 5 minutes to restart but gpu stress test takes about 10-30 seconds in furmark. When i run OCCT psu stress test then it restarts instantly and that also killed one of my usb ports. I have tried to swap ram and connected bare minimum to try but nothing has helped. I also installed new windows and cleared cmos but that didnt help as well. Temps are fine both cpu and gpu wont go above 65 before restart. Sometimes it also restarts just browsing web or smth but usually only under load. I just want other opinion before i buy new PSU.
Specs are
i7 7700K
GTX 970 strix
16gb ADATA XPG GAMMIX D10 DDR4
PSU: Fractal Design Tesla R2 800w gold rated
Maximus VIII Impact by asus

could be between the motherboard or the psu itself..