PC Powers off While Gaming

[Neekoras]

Specs:
i3 6100
Gigabyte H110M-A
XFX RX 470
2TB Barracuda Storage
EVGA 450W Power Supply
Windows 10 Home

All works fine until I start playing a game like CS:GO. Max settings and after less than five minutes, the screen blacks out and the system shuts down. The parts are brand new and while running Prime95, CPU stays below 60c and GPU Stays around or below 90c. I'm certain it is not an overheating issue nor a power issue.

 

[Aeacus]

System shutdown during gaming is mainly caused by 2 issues:
1. Overheating.
2. Insufficient PSU.

RX 470 should be around 60°C to 70°C when gaming, peaking around 80°C. Around 90°C is too hot for your GPU, thus it's normal that you'll see automatic shutdowns at that temp.

Also, your PSU doesn't have good build quality either. When you put near max load onto it, it can simply fail to deliver it and hence why the whole system shuts down.

Note: Prime95 is CPU stress test program. For GPU stress test, look towards MSI Kombustor that comes with MSI Afterburner. Or you can use Unigine Heaven benchmark program instead to test your GPU performance.

 

[Neekoras]

System shutdown during gaming is mainly caused by 2 issues:
1. Overheating.
2. Insufficient PSU.

RX 470 should be around 60°C to 70°C when gaming, peaking around 80°C. Around 90°C is too hot for your GPU, thus it's normal that you'll see automatic shutdowns at that temp.

Also, your PSU doesn't have good build quality either. When you put near max load onto it, it can simply fail to deliver it and hence why the whole system shuts down.

Note: Prime95 is CPU stress test program. For GPU stress test, look towards MSI Kombustor that comes with MSI Afterburner. Or you can use Unigine Heaven benchmark program instead to test your GPU performance.

What do you suggest I do? Should I replace my gpu or buy a new power supply?

 

[Aeacus]

First off, get a better cooling. High temps are good indicator of misused system. It's also the cheapest thing to do.
Further reading: http://www.tomshardware.co.uk/faq/id-1858957/airflow-101-setting-fans-keeping-computer-cool.html

If lowering the temps isn't enough and you still get shutdowns, it's probably your PSU.
Here, i suggest you get a good Tier two PSU, preferably Tier one if you could afford it.
PSU Tier list: http://www.tomshardware.co.uk/forum/id-2547993/psu-tier-list.html

For your system, 500W range PSU will do. Anything from Seasonic is great. Here i suggest either S12II-520, M12II-520 EVO or G-550.
(Got S12II-520 in my AMD build. Specs in my signature. PSU is 3 years old and still running strong. My Haswell build is powered by M12II EVO series and i got PRIME series in my Skylake.)