6700k BSOD until underclocked

[Yoola]

So I have 6700k with ASRock Z170m Pro4S and after unsucessfuly trying to overclock to 4.4GHz (really?) PC didn't boot at all. Clearing CMOS and removing the battery didn't help. I've tried updating UEFI and downgrading to older (supposedly more trusted) versions. At one point in all that 'try that, try that' I came to idea of reinstalling windows because after managing to make it post it'd BSOD randomly with error 'whea_uncorrectable_error' which indicated it's something with CPU. Tried all of the methods from google (setting voltage etc etc) and nothing would make it work. Nope, it'd just randomly BSOD while trying to install windows. All up to the moment when I got the idea of underclocking to 3GHz. Now it works fine but I can't understand who's faulty? Motherboard or CPU? I personally doubt it's CPU because it worked before on 4GHz. ....Idk what to do...?

[WereCat]

Try with only one stick of RAM (try each stick) in every RAM slot... it may be your RAM as well.

 

If not then I would RMA the CPU.

[Yoola]

Just now, WereCat said:

Try with only one stick of RAM (try each stick) in every RAM slot... it may be your RAM as well.

 

If not then I would RMA the CPU.

Did all the tests with only one stick and even switching the slots and nothing made difference until underclocking it. 

[WereCat]

5 minutes ago, Yoola said:

Did all the tests with only one stick and even switching the slots and nothing made difference until underclocking it. 

If motherboard was faulty and you are getting it stable at 3GHz that would mean that the VRMs on the motherboard are bad but usualy it would work at stock speeds and VRMs would overheat.

So my bet is that CPU is screwd somehow. I would RMA it.

 

EDIT:

One more suggestion.

Underclock your RAM by a lot and see if you can run CPU at stock speeds. If it will work your memory controller on CPU is screwd.

[Yoola]

So I had to tinker with CPU voltage to make it stable. Setting UEFI defaults and clearing CMOS didn't do shiet about it. I thought if you set it to default it'll make if good enough to boot safely. Or it's just poor ASRock quality.