Report: Not all PSUs support Haswell's low-power states

So you heard the news: Intel's Haswell processors, known officially as 4th Generation Core, are coming out on June 3. Users hoping to upgrade will have to set aside some cash for a new processor, a compatible motherboard... and perhaps a new power supply, as well.

Indeed, according to the guys at VR-Zone, Haswell may not play nice with some existing "bargain basement" PSUs. That's because the chip's C6/C7 power states apparently require a minimum load of 0.05 amps on the 12V2 rail. The site says not all PSUs have the appropriate circuitry to let the processor sip that little power without the system becoming "unstable" or shutting down. Current Sandy Bridge and Ivy Bridge processors suck a lot more juice—0.5 amps, to be precise—in their low-power states, and meeting that requirement supposedly requires less complex circuitry inside the PSU.

Okay, no big deal. Just check your PSU's specs to make sure it complies, right? You can try, but VR-Zone says that may not be so simple. "PSU manufacturers (even the enthusiast grade ones) do not usually report the minimum load on their spec sheets," the site explains. Sure enough, the tech specs and manuals on Corsair's website don't mention minimum load—and if Corsair doesn't do it, I doubt cheap and no-name manufacturers bother.

I'm not sure how much truth there is to all of this, but in any case, VR-Zone says motherboard makers "have been told" (presumably by Intel) to include a BIOS setting that disables Haswell's C6/C7 power states. I guess folks with old and inadequate power supplies may have to live with higher idle power consumption until they replace them.

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