What setting in the bios do I need to set in order for my cpu to reduce voltage when idle?

I'm using manual mode, I don't want to use offset mode, because it's giving me problems, I don't like the fact that when you lower the offset voltage it also lowers the voltage when the multiplier is at 16, plus when I reduce the offset by -5 and reboot the voltage is at 1.026 which is not enough for my 3570k 4.5ghz overclock, which causes the bios to freeze

I did disable Asus Multicore Enhancement and enable Intel speedstep, my core multiplier is down clocking, but the voltage is not, any ideas?

Is offset mode the only thing I can use to lower my voltage when idle?