I ran furmark with gpuz for about one hour, results where the same with oc bios @ 105% or new bios @118% : freq, temps, fps, power draw...
And impossible to push gpu freq more than +110 without crash, with any bios.
I'm surprised that i achieve to get better results by flashing a bios from another brand and model, but to risky for daily use !
That's why i think it's bios related, an update can do that in my opinion (not an expert)
(And sorry for my poor english, i'm french !)
Edit : after all, it is even a beast ! But i like to push to the ultimate limit !