I tried to revert my overclock back to stock. So I clicked restore to defaults (revert to 3.4ghz). In the BIOS the settings are clearly set as stock. However the previous o.c. cpu frequency (4.4ghz) still remains.
i5-3570k gigabyte z77x-ud3h
More aboutcannot revert default settings
you can use the reset jumper pin on your MB, or remove the cmos battery (for a couple of mins) and see if that works.