Ahh, I understand better now. Yes, you might have to tinker with the bios. I can't help you too much with that, but you should be able to download your bios, change the settings, and reflash it. Just make sure your OC is rock solid stable, and keep a copy of the stock bios just in case.
Edit. Use NiBitor to change bios settings.
NVIDIA BIOS Editor (NiBiTor) v6.01 Program Released :: mvk.tech :: NVIDIA GeForce GTX 580 570 560 460 ATI Radeon HD 6970 6950 6870 5970 :: MVKTech :: On the Edge of Technology