If you recently made an upgrade to the Core i7 system you may found that your older power supply may not able to support the C6 power saving feature that is found in the Nahalem processor. The C6 power saving turns of the core clock, PLL, and the caches. As a result, it is able to lower the core voltage even lower than the C4 state. It is estimated that the C6 uses about 300% less power than the C4.

Despite the fact that many of the older power supplies may have enough wattage and connectors for the Core i7, they do not have the necessary engineering to enter the C6 state. If you enable the C6 state with these power supplies, you may encounter problems such as system constantly restarting. The majority of the power supplies on the market are still catching up with Nahalem so when you shop for a power supply, be sure to look for the one that will support C6 state.



Link: Bjorn3D