I upgraded my PC about two weeks ago, except the power supply and optical drive, but it shuts down unexpectedly when I play my games for about an hour. My specs are: Gigabyte ga-970a-ud3p for the motherboard, AMD FX 6300 for the cpu, Sapphire Radeon r9 270x 4GB, and my PSU is a Xion 700w. Is my...