Sign in with
Sign up | Sign in

Unlocking AMD CPU Cores Safe Say Mobo Makers

By - Source: Tom's Hardware US | B 47 comments

While browsing through motherboards at Computex, several manufacturers were quick to tell us some details about the recently released dual-core Phenom II CPUs from AMD.

Two motherboard makers told us at the show that AMD's new processors are safe when unlocking disabled cores. In fact, one motherboard maker even told us that when you unlock the disabled cores, they run at slower frequencies than the normal cores.

This is of course all incorrect, and it is indeed not a safe guarantee when you unlock the disabled cores. The reason for this is that the disabled cores are turned off for a reason: they failed factory tests. Cores can fail for any number of reasons, including defects in the silicon, problems running at full frequency, or a bug introduced during manufacturing.

Both AMD and Intel disable CPU cores for this very reason.

When you unlock the disabled cores, they will run at full processor frequency, since you cannot run each core at different speeds. While you may see initial gains and benefits from turning a dual-core CPU into a quad-core CPU, you may introduce instability into your system. Things may corrupt, calculate incorrectly or even crash.

Despite what we were told, we still recommend that if you're going to unlock disabled cores, do so with caution in mind--there is always a risk that something will go wrong.

Display 47 Comments.
This thread is closed for comments
  • 0 Hide
    hunter315 , June 5, 2009 8:15 PM
    All of the Phenom II's are identical designs, the best ones end up as 955s and the defective ones end up as 8xx X4s, 7xx X3s, and 5xx X2s. So you only have disabled cores if you bought a phenom. I dont know which Intels have disabled cores.
  • 0 Hide
    tweak13 , June 5, 2009 8:22 PM
    hunter315All of the Phenom II's are identical designs, the best ones end up as 955s and the defective ones end up as 8xx X4s, 7xx X3s, and 5xx X2s. So you only have disabled cores if you bought a phenom. I dont know which Intels have disabled cores.


    very interesting, thanks.
  • 2 Hide
    w4ffles , June 5, 2009 8:27 PM
    I'd like to know where those representatives got their "facts".

    AMD disables cores and sells them in a lower segment because it's more financially sound than just tossing them out.

    I've never heard of Intel disabling cores, but I wouldn't be surprised if some of the dual-core CPUs were like that.
  • 1 Hide
    edeawillrule , June 5, 2009 8:34 PM
    What Intel does is use dual core chips that have a defective core as single core celerons. Also in the case of core solo chips (Core 2 Solo chips I'm not sure about) they were dual core with one core disabled.
  • 2 Hide
    kingnoobe , June 5, 2009 8:34 PM
    I can't see why intel wouldn't. It makes perfect business sense. To simply disable the faulty cores, when the others are perfectly fine.
  • 3 Hide
    ThisIsMe , June 5, 2009 8:45 PM
    Intel wouldn't because they do not use a true quad core chip. It's actually two dual core chips. They couldn't disable a core from one dual core set and disable another core from the other dual core set because it wouldn't make sense from a performance standpoint.

    If they disabled both cores from one dual core side I guess that would work, but would be horribly inefficient, unless they only used this for one specific model and made the rest regular dual cores.
  • 2 Hide
    scooterlibby , June 5, 2009 8:52 PM
    Anand said this loophole will close fast (BIOS updates, clearing of inventory with stable 3rd and 4th cores), so you have to get a Phenom II X2 very soon and make sure you have a mobo with a BIOS that can still unlock. Even then it's not guaranteed to be stable, but I say go for it if you can pull the trigger now and know you're getting the right mobo.
  • 4 Hide
    computabug , June 5, 2009 9:09 PM
    I'll unlock it for a few months while it's my gaming rig :)  When it goes outdated, I'll give it to my parents and lock the cores again :p 
  • -7 Hide
    haricotvert , June 5, 2009 9:46 PM
    Doing ANYTHING to a CPU outside the rated specs can potentially damage it, and will definitely void your warranty.

    How do you think the cores were turned off in the first place? They were fused. One can never perfectly undo something with software (i.e. BIOS settings) that was PHYSICALLY altered to start with.

    Just buy a quad-core if you want a quad-core. Save yourself the headache, risk, and uncertainty.

    Also, cores are not turned off simply for binning purposes or because they "failed factory tests." This is completely untrue. Do some dual- and triple-core processors actually have faulty cores that are turned off? Yes. Do all of them? No. Especially as wafer manufacturing processes improve, you end up with a lot of good dies all with 4 cores perfect.

    AMD intentionally disables even good cores simply so they can have product lines in a different market segment. Why build an entirely new architecture of 45nm chips for dual cores when you can just fuse 2 perfectly good cores, slap it in a box, and put a $75 price tag on it? Some people just do not need a Phenom II 955 but would love a Phenom II 550.

    Tom's needs to do their homework before committing pen to paper.
  • 0 Hide
    cangelini , June 5, 2009 9:59 PM
    scooterlibbyAnand said this loophole will close fast (BIOS updates, clearing of inventory with stable 3rd and 4th cores), so you have to get a Phenom II X2 very soon and make sure you have a mobo with a BIOS that can still unlock. Even then it's not guaranteed to be stable, but I say go for it if you can pull the trigger now and know you're getting the right mobo.


    It was supposed to have closed a long time ago. That isn't stopping motherboard vendors from dragging their feet on BIOS updates, and end-users aren't forced to flash their BIOSes, essentially disabling the capability. So long as AMD doesn't disable this at a processor-level, people will continue trying it and, in some cases, succeeding.
  • 2 Hide
    NuclearShadow , June 5, 2009 10:24 PM
    I think anyone who has any of these CPU's should give it a try. If they find it to be unstable then they can just change it back and they have lost nothing. If it works then its pure gain.
  • 0 Hide
    DjEaZy , June 5, 2009 10:36 PM
    ... and the L3 cache comes handy...
  • -4 Hide
    witcherx , June 5, 2009 10:49 PM
    haricotvertDoing ANYTHING to a CPU outside the rated specs can potentially damage it, and will definitely void your warranty.How do you think the cores were turned off in the first place? They were fused. One can never perfectly undo something with software (i.e. BIOS settings) that was PHYSICALLY altered to start with.Just buy a quad-core if you want a quad-core. Save yourself the headache, risk, and uncertainty.Also, cores are not turned off simply for binning purposes or because they "failed factory tests." This is completely untrue. Do some dual- and triple-core processors actually have faulty cores that are turned off? Yes. Do all of them? No. Especially as wafer manufacturing processes improve, you end up with a lot of good dies all with 4 cores perfect.AMD intentionally disables even good cores simply so they can have product lines in a different market segment. Why build an entirely new architecture of 45nm chips for dual cores when you can just fuse 2 perfectly good cores, slap it in a box, and put a $75 price tag on it? Some people just do not need a Phenom II 955 but would love a Phenom II 550.Tom's needs to do their homework before committing pen to paper.

    A true parental lock... :) 
  • -4 Hide
    witcherx , June 5, 2009 10:50 PM
    computabugI'll unlock it for a few months while it's my gaming rig When it goes outdated, I'll give it to my parents and lock the cores again


    A true parental lock... :) 
  • 4 Hide
    zonker , June 5, 2009 11:04 PM
    THIS ARTICLE IS INCORRECT.

    On all Phenom II processors you can adjust the frequency of each core individually using AMD overdrive. This is well known to anyone who overclocks AMD cpus.

    And it is safe to unlock extra cores in the context that it 'will not damage your hardware'. Instability is always an issue when running outside manufactures specs. So the only valid point this article has is.. 'warning unlocked cores might not be 100% stable'.. Thanks, but we already knew that.
  • 0 Hide
    MU_Engineer , June 5, 2009 11:11 PM
    w4fflesI'd like to know where those representatives got their "facts".AMD disables cores and sells them in a lower segment because it's more financially sound than just tossing them out.I've never heard of Intel disabling cores, but I wouldn't be surprised if some of the dual-core CPUs were like that.


    A bunch of single-core Core 2-based Celerons are dual-core chips with one core turned off. Core Solos were Core Duos with a turned-off die. The Xeon E5502 is a dual-core made from a quad-core die.
  • 2 Hide
    Anonymous , June 5, 2009 11:18 PM
    Yes intel does the same thing, they all do. Why trash a 90% good processor when you can just disable 10% and sell it at a lower price point. You get $0 throwing it away.

    These companies also disable perfectly good chips to meet demand of lower priced parts.

    If you make 1000 processors and 900 of them bin at the top speed grade, what do you do, sell 1 processor to the person who can afford it and the 100 cheap ones to entry level buyers. Or do you stamp a lower speed grade on the other 899 top bins and sell them to mid range buyers at a lower price and a hihdered speed rating.

    It makes perfect business sense to sell perfectly good chips with parts disabled to meet lower price segments.

    Thus NOT ALL of them will have bad parts, some of them will be 100% functional. And also NOT ALL of them will be perfectly good parts, some will have bad parts disabled.

    So as with any overclocking of parts, you run them out of spec at your own risk. A lot of the time you will be perfectly fine, sometimes you wont.

Display more comments