Peter, I think it's a lost battle
Zebo, glad I could help. The SL-K890Pro-939 is good for 280-285MHz I guess, that should be enough even for a 3000+ if you don't want to give it too much voltage.
About the NB heatsink, you'll read this in the ClubOC review:
"An active Northbridge proved to be un-necessary since during our tests, it barely emits any heat."
and also:
"Soltek managed to give us some paste on its northbridge, although we must note that the chipset doesn't emit a lot of heat even overclocked."