Well I would guess that google would help there, but all I know is that three boards I used on that socket with those CPUs did not have it and, it was put there to unlock cores to entice you into buying those boards.. (one of which was a Asus M3A32 wifi AP and allowed me to get the 940 to 3.9ghz stable on an NH-D14)
Asrock use it on some, Nvidia put it (under their naming of NCC or something, UCC maybe?) on their last mobo ever, and it was put there soley to unlock cores.