I've been trying to work through Asrock's voltage and frequency voodoo which is much less transparent than I'm used to.
So many "auto" settings that it feels like setting the voltage manually is a lottery.

In my case it turned out the load line calibration setting causing the most confusion - at it's default preset it was pumping up the core voltage too far.
I wonder if they crank these options up "just in case" without considering processor lifespan.

After some tweaking / learning I found it'll do 5Ghz on all cores, at a reasonable voltage (1.25 - 1.35V) without getting too hot.
Which was a relief because to start with I was seeing worse results than the average 8700K owner.

I haven't finished tweaking everything, so tips welcome.

I also need to find software that isn't Prime95 (really painful with 12 thread windows, why have they not updated this??) for stress testing.