Just an observation after reading countless threads from many, many sites, and reinstalling OS's (Win8.1, 7, and Ubuntu 14.04) into an unstable system. My son's Asrock 970 extreme4 failed after 60 days of use, loosing all audio, regardless of OS. Asrock authorized the return and we suffered the cost for shipping. The board we received two weeks later is very unstable and I spent days of configuration changes, bench testing RAM, and throttling the CPU. Same issue every time...the unit would eventually power off on it's own, in under an hours time. No keyboard press or mouse click would bring it back (if it had fallen asleep) and required a total power cycle of the power supply itself to get it to boot again. Simply hitting the power button on the MB would end in "E8" and no video.
Windows Event viewer showed nothing, other than a Critical event after the recent boot that Windows did no shut down properly prior.
Reading one single post from a user stating that the heatsink on his power regulators were "really hot" opened my eyes. I placed my hand hear the regulators and it was HOT. I quickly dug up a 140mm fan and focused it on the motherboard, between the rear connectors and the CPU. When I awoke this morning, the unit was still running Prime95's torture test (15+ hours and counting).
We're calling ASRock today to look for a return, as I shouldn't need to flood the rear of the motherboard with air like this.