Do you have a performance tab in your bios? You enter bios at boot by pressing the F2 key (dont hold it down - just press, release, press release..)
Change CPU voltage from Auto to whatever you need. Dont go too far however. It will increase heat dramatically. If you change CPU voltage it will stay at that level all the time. Some people like it to drop back down to a lower setting for cooler operation, some could care less...
You could instead try increasing Vdroop - this will supply more voltage as load increases without increasing CPU voltage and keeping it high all the time.
Most Intel boards you will not be able to change the vcore or do any overclocking from bios. I am guessing you have done your overclock by software because of this so you will be limited by the voltage it is set too since you cant change it my advice would be to back off your overclock a bit and find a stable number that is the best you can do with a Intel board.