Computer shuts down while gaming with no bluescreen

[TheQuantumLlama]

After playing a graphically intensive game for a bit (anywhere from 2 min to 30 min), my computer shuts down with no warning at all. No BSOD, my computer just shuts down and after about 3 seconds restarts. Using WhoCrashed, I found a couple instances of a "VIDEO_TDR_ERROR" where atikmpag.sys is referenced as the most likely culprit. I don't know how to diagnose this problem as it does not cause a BSOD, although i can reliably cause it by starting a highly intensive game such as Shadow Warrior or Skyrim.
I have tested my CPU with Prime95 for about 3 hours, the load went up to 100% at some points but the temperature never topped 79 C.

Specs:
Intel Core i5-4670K (not OC'd) w/ Cooler Master Hyper 212 EVO
MSI Z87-G45 Gaming
Radeon XFX 6950
Crucial Ballistix Sport 8GB
Thermaltake 500W

 

[DarknessRising]

you must be right then

 

[DarknessRising]

the problem still remains why would it be shutting off the problem i could think of is the psu now do you have another psu to test with?

 

[TheQuantumLlama]

I just called XFX and they told me a couple things: 1)The card should not shut down before at least 100 C. 2)The card is safe to run into the 90's. 3)I can get a new cooler sent to me free of charge without a receipt.
I'm going to attempt to get a new cooler and see if that fixes the problem, also, I may have found someone with a powerful enough PSU to test with. I will continue updating in case you guys care and so that this might help someone else.

 

[oczdude8]

Great, let us know if the new(test) psu fixes the issue.

 

[TheQuantumLlama]

I borrowed a 650W PSU from a friend and everything runs perfectly fine, I can launch any game and play for as long as I like, games that would barely run past the main menu (Shadow Warrior) will now sit staring at massive fires or whatever else graphically intensive I can find without missing a beat. Seems as though I have successfully found my problem, thanks both of you for your help.

 

[oczdude8]

Great