For a few weeks now, we've known that Intel's Haswell processors feature a new sleep state that isn't compatible with all power supplies. Haswell's sleep power draw is substantially lower than that of previous generations, and it can trigger some PSUs' under-voltage protection and force a system reset.
Corsair described the problem more elaborately in an e-mail to us, which reads:
According to Intel's presentation at IDF, the new Haswell processors enter a sleep state called C7 that can drop processor power usage as low as 0.05A. Even if the sleeping CPU is the only load on the +12V rail, most power supplies can handle a load this low. The potential problem comes up when there is still a substantial load on the power supply's non-primary rails (the +3.3V and +5V). If the load on these non-primary rails are above a certain threshold (which varies by PSU), the +12V can go out of spec (voltages greater than +12.6V). If the +12V is out of spec when the motherboard comes out of the sleep state, the PSU's protection may prevent the PSU from running and will cause the power supply to "latch off". This will require the user to cycle the power on their power supply using the power switch on the back of the unit.
Since the news broke, a number of PSU vendors have indicated which of their power supplies fully support Intel's new processors. We covered some of those announcements, but keeping track of all of them has been difficult. In an effort to be thorough—and, you know, to make things easy for everybody—we've spent a few hours compiling compatibility information from all the major PSU vendors.
Before we proceed, we should be clear about one thing: you don't, strictly speaking, need one of these "Haswell-ready" PSUs to build a Haswell system. Corsair told us that it "fully expects" motherboard makers to let users disable the new low-power power state in the firmware. Cooler Master went even further, stating that, to its knowledge, "all mainboard vendors" will disable the new low-power state in their boards by default. In other words, you may never encounter any issues even if you pair a Haswell platform with an incompatible power supply.
That said, Haswell's lower-power sleep state is one of the perks of the new platform. Compared to the prior generation, it cuts minimum sleep power consumption from 6W to about 0.6W. Those kinds of power savings may not add up to much on your power bill, and they probably aren't worth the price of a brand-new PSU. However, if your current unit is already compliant, you might as well enjoy the reduction in sleep power. Also, of course, folks building a Haswell system from scratch are better off getting a compatible unit to begin with.
So, without further ado, here's our big, non-exhaustive list of Haswell-ready power supplies. The information comes directly from PSU vendors, and we've included links to the source announcements in case you want to double-check. You can skip ahead to each PSU vendor's section through this handy index:
...or you let your scroll wheel run wild and go through all the purdy lists below. Whatever floats your boat.
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According to Antec, the following units are "fully compatible" with Haswell:
However, the compatibility of these units "has not been confirmed yet":
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The following Cooler Master units are all listed as "Haswell-ready."
Cooler Master also proposes a workaround for PSUs that may lack support:
Should customers experience problems nevertheless, or would like to enable the advanced power saving mode on older power supplies that might not support it, there is a simple fix. Simply adding a single silent case fan to the system, connected to the power supply, should provide enough additional load to keep the system running in advanced power saving mode. The only disadvantage would be that power savings in idle mode on such a system would only surmount to around 2-3W instead of ~5W.
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All power supplies that use DC-to-DC conversion to power their 3.3V and 5V rails have no problem with Haswell's new low-power state, Corsair says. The following Corsair power supplies all use DC-to-DC conversion and are listed as "100% compatible with Haswell CPUs":
The ones in this second list are marked as "likely compatible" but "currently validating." Corsair explains that it's "still working with Intel on the details of the testing methodology they use to check PSUs for Haswell compatibility."
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Enermax claims all of its current mid-range and high-end PSUs, as well as some older models, use DC-to-DC conversion and can therefore pump out "rock-stable voltages even at 0W load." Here's a list of them:
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OCZ/PC Power & Cooling
The following OCZ/PC Power & Cooling units use DC-to-DC conversion and are marked as "Haswell ready" by the company:
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Seasonic lists these units as "ready for Intel's Haswell processors," although it doesn't go into much detail beyond that:
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As far as I can tell, Silverstone didn't even put up a press release. It simply listed compatible units in a PDF titled, "SilverStone PSU for Haswell support list:"
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According to Thermaltake's compatibility announcement, "most high-end power supplies of Thermaltake are fully compatible with Haswell CPUs." The compatible units are as follows:
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Here's the word from XFX on Haswell compatibility:
XFX power supplies use a +12V design that allows for a minimum of 0A so they will not have an issue with the new low power sleep states allowing the CPU to enter deep sleep mode without any problems. XFX manufacturing partner Seasonic in conjunction with Intel have worked together to confirm that all XFX Pro Series PSUs listed below are compatible with Intel's new 4th generation Core processor family for new CPU upgrades to current systems and future new builds.
And here's the compatibility list:
The firm adds that its XFX Pro Series 450W and 550W units are not Haswell-ready. However, XFX is "working closely with Seasonic to develop a new 550W Gold Pro Series PSU that will be compatible later this year."
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30 comments — Last by BIF at 9:12 PM on 07/05/13
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