PC shutting down after really low FPS

[chill out]

My PC specs is :

CPU : 6100 FX 3.3 GHZ
OS : Windows 7 x64
GPU : 6950 Twin Froze r II MSI
Mother board : Gigabyte 78MLT
Ram : 8 GB Kingston
PSU : Gamma 500W

This issue started one week ago Whenever i game on my PC it starts fine for about 10-15 minutes then it starts to perform at slow motion and at really low FPS then the PC might shut down or perform the same , after quitting the game if i for example watched a normal video file or watched a video on youtube then the PC instantly shuts down after a few second

I changed the motherboard and CPU and inserted a coolermaster fan as the stock fan was really really loud but that didn't change anything

So anyone can help me solving this issue

Edit : I checked GPU Temperatures and GPU Load using GPU-Z before and after two games

Before playing either games the Load was at 0% and the Temp was at 30's C , after playing Batman Arkham Knight the load jumped to 100% and the Temp was above 100c , I then played a lighter game like PES2015 and the load was at about 5-6% but the temp was as high as 100c or above and the temp at idle after playing games is around 70c

 

[Greg Gregorich]

sounds like psu problem.you wanna check your hardware temperature is it new build ,how many monitors you do have.

 

[chill out]

I checked GPU Temperatures and GPU Load using GPU-Z before and after two games

Before playing either games the Load was at 0% and the Temp was at 30's C , after playing Batman Arkham Knight the load jumped to 100% and the Temp was above 100c , I then played a lighter game like PES2015 and the load was at about 5-6% but the temp was as high as 100c or above and the temp at idle after playing games is around 70c

 

[InvalidError]

Did you check temperatures with something like HWInfo/HWMonitor? Crashing performance before a reboot seems to suggest thermal throttling followed by thermal limit trip.

A failing PSU does not typically affect performance, they usually cause crashes, random shutdowns and reboots.

 

[galeener]

You power supply is listed as a tier 5 do not use under any circumstance3 sounds like it may be dieing.
http://www.tomshardware.com/forum/id-2547993/psu-tier-list.html You should always try to use a tier 1 or tier 2 PSU as worse case a tier 3 for a basic system. Your psu may work but its just trouble waiting to happen. If you have had it a while I would say it may be giving up the ghost.

 

[Greg Gregorich]

if temperature are above 100 Celsius you shorting live of the gpu.you wanna find gpu fan speed software. i never let gpu rise more than 70 Celsius and cpu more than 55 Celsius.