Few PSUs support Haswell’s C6/C7 low-power states

We came across an interesting story at VR-Zone about Haswell’s power-supply requirements yesterday. According to that story, some PSUs won’t support the chip’s C6/C7 low-power states because they’re unable to feed less than 0.5 amps through the 12V2 rail.

We can now confirm the accuracy of that story.

An Intel document seen by The Tech Report echoes the gist of that article: Haswell’s C6/C7 states require a minimum load of 0.05 amps on the 12V2 rail, and some power supplies can’t pump out that little juice. Haswell systems powered by incompatible PSUs can run into stability problems. They can also shut off when entering the low-power C6/C7 states, if the PSU’s under- or over-voltage protection kicks in.

As VR-Zone reported, PSU manufacturers rarely publicize their units’ 12V2 rail specifications, so it’s hard to tell which units will support Haswell’s low-power states. However, the PSU selector on Intel’s Reseller Center website includes a list of power supplies, and that list can be sorted by support for a minimum 12V2 load of 0 amps. I count only 23 units with that capability: 19 Corsair models, three InWin units, and a single Seasonic. That isn’t very many at all—though perhaps some unlisted units also have that capability.

In any event, folks without compatible PSUs shouldn’t necessarily worry. We asked Corsair’s Robert Pearce about this issue, and he told us, “I fully expect the [motherboard] companies to disable C6/C7 in the BIOS (though consumers could enable it if they chose to) as there are simply too many PSU’s in the market space which might not work correctly.” That said, Pearce added that Corsair is working to ensure that all of its power supplies support the C6/C7 states. “We believe they already do but are checking,” he said.

Comments closed
    • fantastic
    • 6 years ago

    Please measure power numbers with this enabled AND disabled when you get your chip(s) to review. TIA

    • tipoo
    • 6 years ago

    So what about laptop power supplies and batteries, can they go that low? That seems to me the more important question here.

      • Firestarter
      • 6 years ago

      Do laptops even have a 12v line internally?

    • Krogoth
    • 6 years ago

    Just more marketing BS that PSU manufacturer’s are trying to pick-up, so they can rebrand and retweak their existing designs. They are doing with a feature that is meant for laptops and ultra-portables not desktops. Motherboard manufacturers don’t even bother to set anything other than S1E by default in their power management settings. There’s only handful of PC enthusiast that bother with the power management settings in the BIOS/EFI. Average Joe/OEM’s don’t know or care either. There’s nothing to indicate that Haswell doesn’t support the older power states.

    That’s absolutely nothing to worry about. In the worse case, you just have to change the setting in the BIOS/EFI if you do encounter an issue related to C6/C7 state. If you desperately want to use C6/C7 state with an older PSU. There are a number of quality models where you can adjust the POTs on the 12V to make it work correctly or you could throw in a resistor on the 12V wire to make it work.

      • indeego
      • 6 years ago

      [quote<]That's absolutely nothing to worry about.[/quote<] ... [quote<]"There are a number of quality models where you can adjust the POTs on the 12V to make it work correctly or you could throw in a resistor on the 12V wire to make it work."[/quote<] But of course. This is STANDARD just to add a resistor on the 12V. I don't know why ANYONE would get worked up about this.

        • Krogoth
        • 6 years ago

        Only anal-retentive and/or completist types will stress over C5/C6 business.

        The vast majority simply don’t care or don’t know any better.

          • NeelyCam
          • 6 years ago

          [quote<]Only anal-retentive and/or completist types will stress over C5/C6 business. [/quote<] It's C6/C7! [i<][b<]C6/C7!!![/b<][/i<]

    • gmskking
    • 6 years ago

    Or, you could just skip Haswell.

      • Farting Bob
      • 6 years ago

      Or you could just leave the super low power states disabled in the BIOS. That seems a better option than waiting another 18 months to upgrade when its very likely Haswell’s successor will continue to use the same power states.

        • HisDivineOrder
        • 6 years ago

        If you’re buying a new CPU and motherboard, perhaps you could just buy a new PSU, too. There are a lot more Platinum models out there than even two years ago, so it seems like an ideal time to upgrade to a quieter, more efficient PSU. Just make sure it’s Haswell compatible.

        Perhaps Intel should create a logo program similar to the one that puts SLI or Crossfire on a PSU. They could call it, “Haswell Compatible.”

    • Generic
    • 6 years ago

    “…PSUs won’t support the chip’s C6/C7 low-power states because they’re unable to feed less than 0.5 amps through the 12V2 rail.”

    “…Haswell’s C6/C7 states require a minimum load of 0.05 amps on the 12V2 rail…”

    “…and that list can be sorted by support for a minimum 12V2 load of 0 amps.”

    The first statement makes sense on it’s own, but then a minimum load is mentioned w/ no upper bound for this lower power state; followed by a list of PSUs that can pump volts without any amps?

    Would someone educate this dullard (me) as to what is going on.

      • superjawes
      • 6 years ago

      Voltage (units in Volts or V) is just the electric potential between two points. In the case of a PSU, it’s between the rail and ground (0V).

      Current (units in Amperes, Amps, or A) is the flow of electric charge. For equation purposes, currents use the letter “I”, and current flows from high potential (Voltage) to low.

      Power (units in Watts or W) is V*I.

      So since Haswell is looking to drop into a low power state, the power coming from the 12V2 rail needs to be very low. The voltage isn’t going to change because it is a reference point, so the PSU needs to be designed such that current doesn’t “leak” into the CPU.

      • NeelyCam
      • 6 years ago

      The upper bound for a low-power mode probably isn’t a concern for a PSU capable of pumping out several amps at 12V.

      PSUs have feedback loops to keep the output voltage on target. My guess is that, depending on the design, these feedback loops might get unstable with very low current (=high impedance) loads.

    • barich
    • 6 years ago

    The options for that Intel selector are “N/A” and “Yes.”

    N/A doesn’t mean no. It probably just means that the information for those units is not available.

      • willmore
      • 6 years ago

      Yep, and now that PSU manufacturer and resellers are aware this is an issue, we should see a rush to fill in the entries with valid data.

    • Chrispy_
    • 6 years ago

    [quote<]19 Corsair models, three InWin units, and a single Seasonic.[/quote<] Corsair don't make their own power supplies, they're simply the ODM and companies like Antec/HEC/Seasonic are the actual manufacturers. For this reason, I suspect that several Antec/HEC/Seasonic units are also capable of deliverying 0.05 on the 12V2 rail.

      • Farting Bob
      • 6 years ago

      Also likely is that Corsair were oner of the few companies to tell whoever at Intel built this site that their PSU’s could handle the minimum load. Im sure most decent and fairly modern PSU’s can handle it but because its never mentioned on a spec list the manufacture has to go out of the way to tell sites it does support the super low amperage, or sites have to manually test every PSU themselves.

    • tootercomputer
    • 6 years ago

    A new PSU feature is born: Haswell low-power state compatible, or “Supports Low Power States (LPS).”

    • smilingcrow
    • 6 years ago

    Curious to see what the difference in power consumption is at the wall socket with a desktop system with these new states. I wonder also how difficult is it for a desktop system to reach these states due to all the background services and utilities on most systems.

      • OneArmedScissor
      • 6 years ago

      Probably 1 watt, and largely because of ATX PSU inefficiency. Deeper sleep states are regularly introduced in laptop parts, but disabled in the desktop version.

      Desktops will still get the real benefit of Haswell’s power savings, which is the “in between” state that can switch must faster because of the VRM chip.

    • albundy
    • 6 years ago

    yay! low adoption already predicted by the discouraged/disgruntled!

    on the other hand, i applaud intel for pushing forward like they did when getting rid of legacy ports on their boards several years ago (PCI, IDE, COM and PS/2 ports come to mind).

    • cynan
    • 6 years ago

    Isn’t the easily solution just to disable these low power states in the bios (or equivalent)?

    Edit: I know it mentions that motherboards will ship with these C6/C7 states disabled in the bios in the article, but don’t motherboard bioses normally have the option to enable or disable these states anyway? (Plus, there are probably many more PSUs that support these states that aren’t on the list – This article seems like a bit of a covert ad for Corsair…)

      • peartart
      • 6 years ago

      That’s exactly what will happen. This is news because these are new states for Haswell, so motherboards don’t currently deal with them.

        • cynan
        • 6 years ago

        New motherboards will be required for Haswell anyway (new socket and different power regulation scheme), so how is it relevant whether current motherboards deal with them or not?

    • chuckula
    • 6 years ago

    Haswell is such a huge disappointment. It has been proven to be slower and consume more power than even the pathetic Ivy Bridge, USB 3 needs to be completely disabled so that your USB 3 devices aren’t destroyed, and now Haswell’s defects are causing PSUs to overload and catch fire. Absolutely nothing works with this chip, but Intel is still going to force us to buy them anyway.

    Is Haswell worth an upgrade over your trusty old Athlon XP? Of course not, go with AMD for a real upgrade! Fortunately, Kaveri will soon be here (socket compatible with your Athlon XP board!) and Intel will soon be out of business.

      • superjawes
      • 6 years ago

      chuckula, winner of comments XD

        • nanoflower
        • 6 years ago

        It feels like he isn’t even trying anymore.

          • chuckula
          • 6 years ago

          After a while it becomes second nature!

            • superjawes
            • 6 years ago

            It’s a zen state of commenting few can achieve.

      • anotherengineer
      • 6 years ago

      You would make a good alter ego for NeelyCam.

      • Concupiscence
      • 6 years ago

      Man, North Korea’s PR machine must be getting REALLY hungry.

      • Bensam123
      • 6 years ago

      You guys realize this is blatant fanboism too using extreme amounts of hyperbole and rhetoric all wrapped in a strawman to downplay any sort of issues Intel actually has.

      He was getting downvoted for these comments last week…

        • chuckula
        • 6 years ago

        Come on Bensam123, posting over-the-top completely disingenuous tripe is something that you taught me! I doubt that I’ve ever posted a single troll on here that wasn’t just a caricature of something you have posted in the past…. except that mine are funny and yours are serious.

        Don’t worry, I still post the occasional realistic post to really get under your skin.. go over the Kaveri article where I 100% accurately point out that any version of Kaveri that uses GDDR 5 will either be in an incompatible socket or (more realistically) be a BGA part just like that dreaded Broadwell you mope about so much. You see, I can be serious too, you just don’t like the (accurate) conclusions I draw!

        • superjawes
        • 6 years ago

        Pssssst….it’s satire.

          • Bensam123
          • 6 years ago

          Also known as sarcasm. It’s not sarcasm if you take it so far as to represent your opponents position in order to deceive people reading it, then you insert some issues you wish to downplay into the mix of it. That’s a strawman.

        • NeelyCam
        • 6 years ago

        No – [i<]you're[/i<] the strawman!

          • Bensam123
          • 6 years ago

          You win!

      • tipoo
      • 6 years ago

      Haswell doesn’t even support 3DNow! well over a decade later, for chips sake! AMD is always ahead.

      • Novuake
      • 6 years ago

      You are either very misinformed or ignorent. Take your pick… @chuckula

        • chuckula
        • 6 years ago

        Altitude of Novuake: 100M.
        Altitude of joke: 12,000M.

    • ronch
    • 6 years ago

    First, it was ‘not all’. Now, it’s ‘few’.

    Not that it would matter to me, of course. No plans to upgrade for the next 3 years or so.

    • lilbuddhaman
    • 6 years ago

    I’ve been “out of touch” with the latest greatest CPUs on the market (i’ve got an older i7 @ 4ghz), but is there sufficient boost in performance to justify a purchase on one of these? A new chipset, new power supply, AMD hobbling along; I only see early adopters getting screwed on this, and people looking to upgrade are probably reading this stuff thinking “ugh I gotta replace my PSU too!?”.

    And jumping back to the performance question, we’ve got new consoles coming down the line, which means new games, on new engines. Whose to say that some PS4 port is going to need/want the benefits of the latest greatest? Whose to say that because of some weirdness with AMD-centric coding that we’re going to see negligible gains or just straight gpu-limitations? I don’t think this will come to light with the first wave of releases, but moreso the 2nd wave, where programmers start (finally) taking advantage of the many-cores their new boxes have, and that in turn gets used on PC titles as well. What weirdness will that bring about?

    This whole comment probably belongs in one of the original Haswell stories….

      • superjawes
      • 6 years ago

      [quote<]This whole comment probably belongs in one of the original Haswell stories....[/quote<] lol, usually we hear something along the lines of "is it worth it?" in Haswell threads. We can answer some questions/concerns, though. As mentioned, the desktop versions will probably just ship with C6/C7 states off. Those states are - as others have and will mention - more for the mobile market. That way, [i<]if[/i<] you want those states, you can pick a proper PSU and get it, but it isn't necessary. For the "worth it" question, that depends. I'm on a first-gen i7 920, so it is definitely an upgrade for me since I will get faster speeds on my CPU and faster RAM speeds (the 920 can't really make use of anything above 1066 MHz). Since I'm due for other upgrades as well, Haswell makes a compelling case, considering how close it is. Early adopters probably won't get screwed unless they're upgrading with every single CPU launch, which I don't think is necessary since, as you pointed out, the gains are fairly minimal since most of the development is going into IGPs and lowering power and heat generation. Those are great advancements, but they aren't really going to give you a huge boost to desktop gaming performance.

      • Krogoth
      • 6 years ago

      That i7@4.0Ghz is a still a beast performance-wise.

      The only thing that you will get out of upgrading to something newer is reducing your loaded power consumption and getting newer CPU standards.

        • indeego
        • 6 years ago

        Basically, if you don’t know if you need it… you almost certainly don’t. This has been true on the CPU scene for a while now.

        The people interested in these chips want latest/greatest just cause, want overall fleet power less usage, or want some of the aforementioned extensions.

        The consumer hasn’t been CPU limited in a long while.
        The casual gamer hasn’t been CPU limited in a long while.
        The hard-core gamer/prosumer has justification to get this if it’s the usual 3-year cycle.

    • nanoflower
    • 6 years ago

    I suspect there may be more Seasonic units that meet this new demand. I noticed that my unit isn’t even in the list and there are probably other Seasonic PSUs that are currently being made that aren’t on the list. I think that Corsair is one of those rebadgers that gets most (all?) of their PSUs from other companies like Seasonic/FSP I suspect many others will pass this requirement but either haven’t been tested or haven’t communicated this to Intel.

      • GTVic
      • 6 years ago

      I think the list may only show active products. So a discontinued product like my Corsair HX620W might work. Apparently it is actually a Seasonic model.

      Also, if you read reviews of the HX620W, like most consumer power supplies, all of the 12V rails are virtual and there is actually only a single rail. So it could be that the other rails to the GPU and peripherals are drawing some power during a low power state and might keep the PSU from tripping on the low power state.

      [url<]http://www.tomshardware.com/forum/306437-28-single-rail-multiple-rails-eternal-question-answered[/url<] [url<]http://www.jonnyguru.com/forums/showthread.php?t=3990[/url<]

    • Arclight
    • 6 years ago

    I suspected this would be the case.

      • chuckula
      • 6 years ago

      Krogoth suspected it first!

        • Arclight
        • 6 years ago

        Above article posted 9:39 AM on April 30, 2013

        My comment stating
        I get the sarcasm but we don’t know yet which PSUs are good or not. It might be that even Bronze certified ones aren’t good enough and i believe they are the most numerous in the DIY builds.

        posted Apr 29, 01:47 AM
        [url<]https://techreport.com/news/24728/weekend-shortbread[/url<] Could it be that this time Krogoth was late? I don't expect him to be impressed though.

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