Building a PC isn't enough, here's how to test it!
With a custom gaming PC, especially when you overclock you need to make sure that all of the parts and components in your build are working correctly with a stress test. Is your power supply up to powering the entire computer? How about the CPU and graphics card, are they able to run at 100% without problems? Same goes for your cooling, under heavy load is the PC able to keep cool?
Core Temp: http://www.alcpu.com/CoreTemp/
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Go Kart - Kevin MacLeod (incompetech.com)