PC keeps restarting itself when gaming

Foley9

Prominent
Apr 9, 2017
3
0
510
So i Recently bought Assassins Creed Syndicate but as soon as I launched it and got into the gameplay my PC restarted itself. I thought it may be something to do with the game so I tried launching Football Manager 17 (which had been working fine until now) and this also caused it to restart. I haven't changed any part of my PC for about 2 years so I'm not sure what can have gone wrong.

I've done a fair amount of googling trying to work out what the issue is, but still haven't resolved it.

This is what I've tried so far:
- uninstalled all Nvidia Drivers and reinstalled them
- used HWmonitor to measure temperatures, all seemed ok
- ran prime95, computer ran fine, temps were ok
- ran furmark, temps were ok but it restarted PC after 2 minutes (the longest AC: Syndicate or furmark has lasted is about 30 minutes)
- checked the PSU, voltages on all pins were ok and fans working fine

specs:

Processor: Intel Core i5-4570 3.2GHz Quad-Core Processor
Memory: Kingston HyperX Blu 8GB (2 x 4GB) DDR3-1333 Memory
Storage: Seagate Barracuda 2TB 3.5" 7200RPM Internal Hard Drive
Motherboard: Gigabyte GA-B85M-HD3 Micro ATX LGA1150 Motherboard
GPU: MSI GeForce GTX 970 4GB Twin Frozr V Video Card
PSU: Cooler Master 750W 80+ Gold Certified Fully-Modular ATX Power Supply

I'm really not sure what to try next. I was thinking of putting in my old GTX 660 just to see if it made any difference but I'm clutching at straws here.
 
Solution
GTX 660 140W Maximum Graphics Card Power (W)
GTX 970 145W Maximum Graphics Card Power (W)

they both consume about the same...

you could get a psu and see... it does kind of point to the video card though.. did you buy it from store ? could you get them to test the card?

Foley9

Prominent
Apr 9, 2017
3
0
510


Put in the GTX 660 and ran furmark, it has been running for 45 minutes now without restart.

Does this mean it's my GPU that's faulty OR that the PSU is not failing now as it does not need as much power for a GTX 660 compared to the GTX 970 before?