My PC crashes whenever I play graphically intensive games.

[moorbs]

When I play games such as Black ops 3, The witcher 3, Tomb raider etc. (Sometimes Fallout 4) my PC screen goes black. The sound and programs like skype sometimes carry on but mostly It buzzes or maybe loops. I have to hard reset and sometimes when I turn the PC back on it won't post, sometimes it will post like normal and sometimes it will be 5 times (2 spaced out but quick beeps then 3 quick beeps together).

Is it more likely to be a graphics card or PSU problem? Or motherboard?
I've also already tried a fresh install of windows.

Specs:
PSU: Corsair CX 600W 80+ Bronze (I would buy an EVGA super nova G2 750w to replace)
CPU: Intel i5 4690K slightly overclocked to 4GHz
GPU: EVGA GTX 970 SC ACX 2.0 factory overclocked (I've tried underclocking but it still crashes about as often)
Mobo: Gigabyte Z97M-D3H
Memory: Kingston Fury White Series 8GB (2 x 4GB) DDR3-1866 Memory
Storage: Samsung 850 EVO-Series 500GB 2.5 Solid State Drive
Storage: Toshiba 2TB 7200RPM Internal Hard Drive

Temps: GPU 70-80 degrees C under load
CPU 60 degrees C under load

I'd appreciate any suggestions.

 

[Sergeant_Sneaky]

From the Gigabyte website:
"3 short beep ：basic memory 64K address check error"
"2 short beep ：CMOS Error"

Try resetting your CMOS by removing the battery for at least a minute.
The 3 short beeps seem to be indicating a memory error, I'm not entirely sure but try both sticks of RAM separately in slot 1.

 

[moorbs]

From the Gigabyte website:
"3 short beep ：basic memory 64K address check error"
"2 short beep ：CMOS Error"

Try resetting your CMOS by removing the battery for at least a minute.
The 3 short beeps seem to be indicating a memory error, I'm not entirely sure but try both sticks of RAM separately in slot 1.

Thanks for the reply.
I don't think those error codes correspond to it because it's kind of all at once (but I don't have a processor problem) and I've installed the latest bios.
I'll try out one RAM stick at a time as you suggested, although I could not find any problems in several hours of memtest.