It seems like this any kind of bug in Afterburner or so on..
I've shortly tested with Heavens and the result:
Standard Bios ~ 2120 Clock
ASUS OC BIOS ~ 2500 Clock:
I also thought it couldn't be right because it all was on air.
My question here is:
What could be the cause for the Clock failure?
Shame on me for disappointing you