Possible power supply issues for Intel Haswell CPUs

Subject: Cases and Cooling, Processors | May 1, 2013 - 03:07 PM |
Tagged: power supply, Intel, idle, haswell, c7, c6

I came across an interesting news story posted by The Tech Report this morning that dives into the possibility of problems with Intel's upcoming Haswell processors and currently available power supplies.  Apparently, the new C6 and C7 idle power states that give the new Haswell architecture benefits for low power scenarios place a requirement of receiving a 0.05 amps load on the 12V2 rail.  (That's just 50 milliamps!)  Without that capability, the system can exhibit unstable behavior and a quick look at the power supply selector on Intel's own website is only listing a couple dozen that support the feature. 

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This table from VR-Zone, the source of the information initially, shows the difference between the requirements for 3rd (Ivy Bridge) and 4th generation (Haswell) processors.  The shift is an order of magnitude and is quite a dramatic change for PSU vendors.  Users of Corsair power supplies will be glad to know that among those listed with support on the Intel website linked above were mostly Corsair units!

A potential side effect of this problem might be that motherboard vendors simply disable those sleep states by default.  I don't imagine that will be a problem for PC builders anyway since most desktop users aren't really worried about the extremely small differences in power consumption they offer.  For mobile users and upcoming Haswell notebook designs the increase in battery life is crucial though and Intel has surely been monitoring those power supplies closely. 

I asked our in-house power supply guru, Lee Garbutt, who is responsible for all of the awesome power supply reviews on pcper.com, what he thought about this issue.  He thinks the reason more power supplies don't support it already is for power efficiency concerns:

Most all PSUs have traditionally required "some load" on the various outputs to attain good voltage regulation and/or not shut down. Not very many PSUs are designed yet to operate with no load, especially on the critical +12V output. One of the reasons for this is efficiency. Its harder to design a PSU to operate correctly with a very low load AND to deliver high efficiency. It would be easy just to add some bleed resistance across the DC outputs to always have a minimal load to keep voltage regulation under control but then that lowers efficiency.


Source: Tech Report

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May 2, 2013 | 02:09 AM - Posted by Tim Verry

Dang that means I'll have to replace my Antec TruePower Trio 650W--that thing has been through like 3 overhauls. I always thought  I'd have to replace it because of SLI/Crossfire + more hardware and not just because it couldn't deliver too little power ;). I guess I could just not use the new sleep states if I go Haswell though as the article says :).

May 2, 2013 | 09:00 PM - Posted by Anonymous (not verified)

Or you could just turn off Cstates? I already have them off as it is.

May 3, 2013 | 05:58 AM - Posted by Tim Verry

Yeah, I know--I hardly ever turn my PC off, just to sleep and better power efficiency is always a good thing though. It may just be time (or perfect excuse? ;) ) to retire the trusty PSU--I have had it for quite a few years now :).

May 2, 2013 | 09:34 AM - Posted by Anonymous (not verified)

Interesting that the new Titanium spec for efficiency starts to make it's way to market around the release of Haswell. The new Titanium PSU spec if for low load. 90% efficiency at 10% load.

May 3, 2013 | 01:05 PM - Posted by anonymous (not verified)

Is there a way to test your psu? I have been collecting parts for a Haswell build. I got a nice deal on this Ultra x4 850watt PSU http://www.tigerdirect.com/applications/SearchTools/item-details.asp?Edp... I would like to know if it works with the c6/c7? I have this tester for checking psus http://www.tigerdirect.com/applications/SearchTools/item-details.asp?Edp... I don't think will help for this question.

September 17, 2013 | 01:52 PM - Posted by Anonymous (not verified)

So do all of the psu's on the list given by intel on the link above? Or is it just a few; because i thought i saw the TruePower Trio TP3-650 on the list.

October 1, 2013 | 11:41 AM - Posted by mehtab singh (not verified)

please suggest .
4th gen haswell laptop .purches
or not

4th gen haswell is good or not

plz tell me
am i can purches this haswell laptop or not

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