I realize this thread is over a year old, but I am having the same issue: Same CPU & motherboard.
I've gone through the steps provided by mdocod to no success. No matter what voltage I apply the 9590 refuses to go over 4.8GHz stable. System freezes outright when stability testing for 4.9GHz or higher. I've tested every step of voltage all the way to 1.55 and anything higher refuses to even boot; it'll POST but then it's stuck with the DOS cursor flashing in the top-left. LLC is as tightly locked in at the same voltage for both idle and load as can be as monitored with CPU-Z. Turbo never wants to activate if I enable it and load a single core. I'm not messing with base clock at all. Spread Spectrum and all CPU power-saving features are disabled. I have G.Skill Trident X 2x8GB 2400MHz at stock XMP timings/speed. I've not messed with the NB/HT speeds/voltages yet. I've had an 1100T overclocked to 4.4GHz stable on this same motherboard with a 1.6vcore (likely didn't need to be that high, it was a quick dirty OC). The only other board I have to work with is a Biostar 990FX Extreme which has been seen to get an 8350 to 5.5GHz at 1.68vcore (stability was untested in the video). For stock full load across all cores my core temp doesn't go over 45c and idles at 20c (CoolerMaster Glacer 240L with fans ramping up from ~40% to ~80%) so I have plenty of thermal margin (25c under load according to AMD Overdrive). And for whatever reason enabling manual overclock has been producing odd issues at random on occasion like Aero not working at boot after some setting changes, but works after reboot.
My questions are as follows:
What are the odds my CPU isn't working up to spec let alone anything higher?
Should I dare testing the 9590 on the Biostar?
What are the odds it's the motherboard?
I'm used to seeing outright BSODs when overclocking proves unstable; why is the system freezing instead here, and is that normal?
Why is it refusing to boot with more than 1.55 volts when it's technically capable of more?
And above all else; what should be the first thing I do to investigate this further?