I had the same problem with the following setup:
AMD FX Series FX-8320 (boxed cooler)
8GB (2x 4096MB) Corsair Vengeance Black DDR3-1866
ASRock 970 Extreme4
I underclocked, overvolted, tested with only one RAM module in varying ports, tested different RAM, switched the Mainboard and the Processor separately with identical newly purchased parts. Tested another power supply.
Prime would stop workers after seconds due to faulty rounding and the PC would crash randomly.
I was so relieved when I read about the 2.3 BIOS, sadly it has not resolved my problem. Prime will now work longer and instead of stopping singly workers, the system crashes imediately with a BSOD after about 30 to 60 seconds. I tried overvolting the RAM to 1.65V and lowering its frequency to 1300MHz. I also tried raising the already high Vcore (1.4V standard) to 1.45V - but no luck.
Because I already switched every part ond others have the same problems with this Mobo I am really not pleased with AsRock this time. How can you put a CPU on the list of supported processors when it obviously does not function properly?
Any further hints are greatly appreciated. :)