So this only happens during video games, but the comp will randomly turn off. It use to happen only during newer video games, now it does it on League of Legends. I remember during SC2 it'd shutoff as soon as it hit the menu screen and it seems to have worsen.
It's a MSI Radeon HD 7970. I figured it may be overheating but both of the fans are working and when I check the temp before it shuts off it is usually about 39-42c. The PSU is 630 watts and about 4 or 5 years old.
You should replace a PSU about every four or five years yes.
They become less efficient through use, and less stable when it comes to producing power. due to the age of components inside and heat produced.
They start off glitching and then slowly get worse and more frequent.
Shut down of the system, BSODS, and resetting of your computer when heavy power load is required from them.
Overclocking of components can cause the same problem.
And backing any overclock off components in the system if you have overclocked components may stabilize the system under heavy power usage..