Intermittent power off of the computer. What could be the problem?

Question

Batteries

The bottom line is that with a heavy load in the game, with a full check of the antivirus (Kaspersky), viewing the same twitch, the PC turns off, i.e. the screen goes blank, coolers stop, etc.
The problem is definitely NOT with the PSU (they put another one, everything is the same), the temperature (it turns off at standard *in the game* 75-80 on the processor, it used to work with such a PC), the power cable (also put another one) and the motherboard (bought a few months ago).
Components:
Video card - GeForce GTX 650 Ti
Processor - AMD Fx-4170
RAM - 8gb
Motherboard - ASRock N68-GS4 FX R2.0
Operating system - Windows 7 Home extended Service pack 1
Power supply - Cougar STE 600W [CGR ST-600 ]
HDD - 1tb

Answer 1

Give the load on the percent and separately on the video. And also do all memory tests. If nothing comes to light, then it remains to sin for (time) clicking.

Answer 2

You carefully examined the power cable, very often it can be frayed at the bends and short.

Answer 3

You did not write how exactly the computer turns off. If this is a banal power failure, then usually at the next start, before starting up normally, the OS conducts a self-test - it cleans up everything that did not complete correctly in the previous session. If there is such a self-test the next time you turn it on, it means that the matter is still in the power supply, regardless of the fact that you deny it (there simply cannot be another reason).
The second option is when the shutdown occurs regularly, with the closing of the running user software, system processes and services. This is also possible from hardware (for example, overheating sensors or periodic spontaneous closure of the power button from random shocks), but most likely softwarecause. In this case, use the recovery subsystem - roll back to a restore point created before the occurrence of this disaster. If system partition recovery is not enabled or configured - well, then use a backup copy or reinstall the OS.
In order not to miss anything, you can also assume remote power management of your computer through the network (some BIOSes have this option), but this is already quite exotic.