Not all power supplies will support Haswell's zero load design, Enermax says.
Intel's Haswell refresh is coming, and when it does, it will deliver better performance, much improved integrated graphics , and superior power efficiency that, according to Enermax, only a handful of power supplies are able to take advantage of. Enermax is referring to the new C6 and C7 states that are able to reduce CPU power consumption to a mere 0.05A. Some Ivy Bridge chips draw up to ten times more in a minimum power state.
According to Enermax, only power supplies that support ultra low loads will do that feature any good.
"The positive progress of the CPU technology is subject to certain restrictions, because only few power supplies will be able to deliver stable voltages at such low loads," Enermax says. "End users are therefore groping in the dark with no clues if their own power supply will be compatible with the new energy functions of Intel Haswell CPUs. PSU manufacturers usually do not state the possible minimum load of their products."
Let's be clear, this doesn't mean your current power supply won't work with a Haswell processor, Enermax is just saying that certain models may or may not be able to utilize the so-called zero load design. If a PSU isn't able to supply 0.05A on the +12V rail, then entering a C6 or C7 state could trigger Under Voltage Protection (UVP), in which case you'd probably need to jump in the BIOS and disable the C6/C7 function.
Enermax claims you won't have to worry about that on all of its PSUs dating back to the Revolution85+ Series released in 2008, which "deliver rock-stable voltages even at 0W load," and are therefore able to fully take advantage of Haswell. For a list of specific models, both old and new, just take a peek on Enermax's website .