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AMD Hardware Hacking Upgrades Hardware

Hidden Cores On Phenom CPUs Can Be Unlocked 251

Posted by CmdrTaco
from the what-could-possibly-go-wrong dept.
An anonymous reader writes "One of the major ways a semiconductor manufacturer manages to make the most of its chips is through binning. Chips able to cope with high clock speeds with all cores running end up as premium product lines, while others end up as models rated at lower speed grades, or with fewer cores. In the case of AMD's Phenom CPUs, dual and triple core models are quad cores with some disabled, while some newer quad core CPUs are actually six core models with two disabled. To this end both ASUS and MSI have announced that they have modified versions of AMD 890FX- and 890GX-based motherboards to unlock these hidden cores. Much like overclocking, there is no guarantee that you will gain anything by unlocking the hidden cores — everything depends on just why your CPU ended up in a certain product line."
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Hidden Cores On Phenom CPUs Can Be Unlocked

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  • by gehrehmee (16338) on Tuesday April 20, 2010 @11:56AM (#31911392) Homepage

    Just a thought, maybe Linux could be aware of what those cores look like, and what their sensitivities to temperature are.... and change the amount or type of work pushed to that core? Although I suppose heat from the other cores would most likely transmit very quick to the "zombie" core. Any CPUs have seperate temperature tracking per core?

  • by MBGMorden (803437) on Tuesday April 20, 2010 @12:03PM (#31911540)

    It depends on the maturity of the product. Often cases early on there is a legitimate need to reuse chips with flawed cores so they are disabled and sold as such. Later in the product cycle though, the demand is still there for lower cored versions, but manufacturing has often caught up to the point where there simply aren't enough flawed versions to fill demand for the limited versions. Result is that when the quota of flawed runs short, perfectly good chips are limited in the same way to fill the gap.

    Later in the product line it might end up that only 20% of the lower priced chips have any flaws at all. For those people who want to tinker, it's often worth while to at least check and see if their chips will run ok when then turn the rest of them on. They stand to gain some performance if it works, and if not - eh, they paid for the slower version anyways (the only issue I take with this is when I see Negwegg reviews or forum posts claiming that they were returning the chip because it "didn't overclock far enough").

    It's not something I really bother with anymore (as I've gotten older as long as the computer keeps running I'm happy), but I remember enjoying the whole overclocking scene ~10 years ago and wouldn't begrudge the new cheap teenagers of the same fun I had :).

  • by tlhIngan (30335) <(ten.frow) (ta) (todhsals)> on Tuesday April 20, 2010 @12:15PM (#31911732)

    You're showing a complete lack of understanding as to how processors are rated and sold. AMD determines they need to meet a certain quota for each model of CPU. If it works out and all of the CPUs in their 1 million unit run works flawlessly, they will maximize their profit by disabling some of them and selling them for less money to account for that market without flooding the market with their top performing part.

    True, but there's also a good possibility that the your part wasn't binned to fulfill an order. Chips go through a severe set of stress tests that often exceed what will be encountered in practical use. During these tests, it may be revealed that a core doesn't function properly or well enough (it gives bad results) to qualify. All chips go through that, and that's why there's many redundant structures on a chip (to improve yields). (Sony PS3 has 7 SPUs when they build 8 on a chip, Xbox360's got 3 PowerPC cores even though it has 4, Intel disables cache lines and/or functional units, etc. etc. etc.)

    So the question is, are those cores disabled because AMD had extra parts and an outstanding order they could fulfill? Or are there actually potential issues that may only be revealed under certain loads? FOr the most part, it just means a game crashes a bit more often than usual (since mission critical servers never do wierd things like this - the money saved isn't worth the potential for extra downtime), or maybe a file gets corrupted. Or worse, your disk gets corrupted.

    Plus, AMD's historically been supply-bound and unable to fulfill demand for their product, so there's a potential that instead of getting a binned part, it's actually one that failed their test patterns.

    And yes, you see the same behavior with flash chips - NAND flash traditionally ships with bad blocks, and the majority of those can probably be erased and used quite safely (having accidentally destroyed the bad block information before due to buggy software...), but you never can tell why it was marked bad in the first place.

  • by Joce640k (829181) on Tuesday April 20, 2010 @12:23PM (#31911832) Homepage

    History has shown that there's a pretty good chance that it _was_ binned for marketing reasons.

    (ie. In many previous CPUs, graphics cards, etc. you had to be pretty unlucky to get one which didn't work perfectly)

  • Oh hell yeah... (Score:5, Interesting)

    by DG (989) on Tuesday April 20, 2010 @01:06PM (#31912480) Homepage Journal

    For a while I was selling race car / high performance street car suspension systems.

    I had discovered that 90% of the aftermarket shocks being sold as performance upgrades were actually crap. The customer is really not qualified to properly evaluate a shock valving and so it is very difficult for them to differentiate between a proper performance shock and a juiced-up pogo stick.

    I started putting shocks on a device called a "shock dyno" (which measures the forces produced by the shock at different shaft speeds) and discovered an absolute parade of horror. Details can be read at http://farnorthracing.com/autocross_secrets6.html [farnorthracing.com]

    To get the good stuff you needed to be paying upwards of $3000 per corner (so $12000 per car) which is far, far out of the price range of most customers.

    So I was building packages based on a brand of shock that was pretty decent and much cheaper. Even though the base design was solid, it still suffered from manufacturing variations. To get around this, I would buy batches and then dyno the lot. Shocks that were close to each other became matched sets, and I'd tweak the adjusters on the shock to ensure each pair was as closely matched as possible. On top of that, I designed some hardware to resolve some other tricky problems typical of the off-the-shelf aftermarket designs, and only used the best bang for the buck components to build them.

    When done, I provided a race-quality suspension system, dyno-matched (and it came with the data sheets to prove it) that was very nearly the equal of the $3000/corner systems, for about $500/corner. I say "nearly" the equal because the adjusters on my shocks worked nowhere near as well as the adjusters on the expensive shocks, but in terms of absolute performance, they were effectively identical.

    There was almost no markup in these parts; I was hoping to make it up on volume and I knew the customer base was price-sensitive.

    These suspensions were INCREDIBLE deals. There was nothing else like it anywhere for anything less than 5 times the price, and unlike all the cheaper stuff, I could prove that it worked. What's more, I could run the cheaper stuff on my dyno and prove that it DIDN'T work; that it was categorically JUNK.

    I sold almost none of them, and the universal complaint was "too expensive".

    Even when I opened up the books, showed what I was paying for the components, explained why *this* part instead of *that* part, explained every single design decision and proved why it could not be made any cheaper without compromising the functionality, over and over again potential customers would choose to buy non-functional (but shiny) JUNK over functional parts based solely on price.

    It was mind-boggling, and eventually I just said to hell with it and found something else to do.

    The chip manufacturers are right on the ball here. If I were them, I'd be encouraging the creation of these kinds of motherboards and rather than down-rating the high end parts to make mid/low end, I'd be cherry-picking the best ones for the high end and defaulting the output of my fab runs right to the mid/low end SKUs. In fact, I'd be tempted to DESTROY any chip with a bad core and ensure that all the low-end chips were fully functional - specifically to build a reputation for being "overclocker-friendly".

    You can't make money off what you DON'T sell. Believe me, I know.

    DG

  • by ByOhTek (1181381) on Tuesday April 20, 2010 @01:21PM (#31912698) Journal

    What test suite would you use though?

    I seriously doubt prime95 is comprehensive enough to cover all CPU operation.

    How do you ensure the test runs on the knocked-out core?

    Note: I'm not saying this to be sarcastic or suggest it is a reason to not try unlocking the cores - I'm actually curious (*looks at 65W dual core Phenom II*)

  • by Anonymous Coward on Tuesday April 20, 2010 @01:30PM (#31912860)

    I recently bought a Phenom 555 and an Asus motherboard that allowed me to unlock the two dormant cores. No doubt one is taking a chance when doing something like this, but personally I think it is a marketing gimmick by AMD who is appealing to the "hardware hacking enthusiast". Anyway, I put my new machine together and was amazed at how easy and obvious it was to unlock the two cores. On first boot I noticed a message saying "Hit F? to enter ACC". Doing so would have taken me to a menu where I could unlock my cores. Instead I entered the bios settings, went to the "Processor" tab, set ACC to "enabled" which then revealed a setting titled "Number of cores" which had a value of 2. I set the "Number of cores" to 4 and rebooted. Upon reboot the bios splash screen said "4 cores enabled !!!" and had a graphic of a cpu with the number 4 overlaid on it. It was as if it was designed to make it very easy to do and my machine has been running perfectly stable 24/7 for a month now.

    Bottom line is, this is a marketing initiative by AMD aimed at the hardware enthusiast.

  • by Alok (37687) on Tuesday April 20, 2010 @01:37PM (#31912984)

    Many AMD motherboards with 710, 750, or 850 SB (south bridge) support unlocking of cores in BIOS - the feature is called as ACC (advanced clock calibration). In fact, right now I am sitting on an X2 555 trying to decide whether to keep it (and have to spend more on DDR3 as well) or return to store; with the potential to unlock it into an X4 955.

    However, from some accounts AMD was trying to convince motherboard mfrs. to stop offering ACC in newer boards; so the fact that its working on 890 SB now is the actual news (if the article is correct). Not really surprising though, now that users are getting spoilt into having easy ways to potentially unlock cores it would've been pretty hard to stop that and make competing mobos more attractive :-)

  • Re:Oh hell yeah... (Score:3, Interesting)

    by DG (989) on Tuesday April 20, 2010 @02:09PM (#31913468) Homepage Journal

    There were two different types of customer for the $3000/corner parts:

    1. Real Racers who understood the value-add the top line components brought to the table and who would sell their mothers to get that functionality; and

    2. Rich posers who were all about being EXTREEEEM and who were buying the name to impress other rich posers.

    Neither of these markets are very big - but they would spend the money.

    The very, very much larger "budget racer/street driver" market was all about price.

    DG

  • by retchdog (1319261) on Tuesday April 20, 2010 @02:36PM (#31913812) Journal

    I remember when running the "Second Reality" demo (by Future Crew) on my 486, if you hit the desk the computer was on, the particles on screen would jump around to different locations (and occasionally it would crash). I never noticed any other problems with any other software. Granted it was probably the RAM and not CPU, but after seeing this, I was really surprised that the computer worked at all...

  • by ottothecow (600101) <ottothecow@NosPam.gmail.com> on Tuesday April 20, 2010 @04:52PM (#31915468) Homepage
    That would only be true if it was a pure commodity item with no real differances besides grading--think meat...You wouldn't downgrade a bunch of Prime beef to Choice just because your cow ended up being 100% Prime. You would sell everything at Prime price and assume that the Choice market would be filled by farmers who got unlucky and had cows with no prime meat.

    These are not cows--these are high end CPU's, there are two major industry players and they do not make identical products. In this market, you would rather price discriminate. AMD historically has had lower prices than intel but people still buy intel--so there must be more to the story than you are imagining. The key here is that AMD gets to segment their market and price discriminate. Sure, they are selling you 4 cores for 80% of the 4 core price by labeling them as 3 cores, but that means they get to make a 20% premium on people who want guaranteed 4-core functionality.

    I am explaining this poorly--but for someone accusing everyone of having a "poor understanding of economics" you sure seem to be spewing a lot of misinformation (mainly driven by your interpretation of CPUs as a commodity).

  • Re:No, not so much (Score:3, Interesting)

    by electrosoccertux (874415) on Tuesday April 20, 2010 @05:12PM (#31915698)

    and that's why I made the comments about the games. Prime95 is not the only stability test I ran, lol, duh.

    All my applications work fine; I've been running this rig for about 8 months now.
    I don't know why you're so hell-bent on telling me my chip is broken, people get pissed when someone gets something for free it seems...we should tax me since I didn't pay for it.

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