Hidden Cores On Phenom CPUs Can Be Unlocked

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."

Comments

Whatcouldpossiblygowrong

[Linker3000]

Unlocking cores that the manufacturer deems to be flawed - um, yeah.

Unless this is a rehash of when Intel were (alleged?) to be selling 486DX processors as 486SX with perfectly good maths co-processor cores disabled, I think I like my data unscrambled! /Lawn etc.

Re:Whatcouldpossiblygowrong

[qoncept]

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.

Unless this is a rehash of when Intel were (alleged?) to be selling 486DX processors as 486SX with perfectly good maths co-processor cores disabled ...

Uh, yeah, basically that's what the article says.

Re:Whatcouldpossiblygowrong

[Jeng]

Or even cost effective.

Pay more for a better CPU, or pay more for a better motherboard so that you can buy a not as good CPU and hopefully have the functionality of the better CPU.

Re:Whatcouldpossiblygowrong

[MoonBuggy]

They might not necessarily be flawed. It quite probably is a 'rehash' of what Intel were doing, and for good reason:

If all the chips come off the same line, then they might have an average cost of, say, $150. If there's a huge demand for quad-core chips at $200 and little demand for six-core chips at $350 then it's probably going to be more profitable disable two cores, bulk up the stock already consisting of chips with only four working cores, and take the $200 rather than have a chip sitting on a shelf. Thus some quad-cores are perfectly good six-cores, others aren't. They couldn't, however, afford to market all the six-core chips at $200 because the yield would be too low - there'd be nothing to do with all the faulty ones, thus pushing the average cost above $150.

Re:Whatcouldpossiblygowrong

[MrNaz]

Right. And given that there is *always* a yield rate somewhere below 100, it's a guarantee that not all of the partially disabled parts are in actual fact fully working. You'd have no way of knowing if you do. In fact, given that the yields are private information, you don't even know the *probability* that your unlocked unit will work properly.

The manufacturer will *always* bin the partially flawed parts as their low end units first. They will only use intentionally crippled units to fill the low end volumes if they run out of partially flawed units. Historical experience with yields indicates that they're more likely to get not enough fully functional units than they need. This was the case with single core parts, and I'd assume it's even more the case with multi-core parts, becoming more of a problem as core counts increase. I doubt AMD or Intel have the latitude to pick and choose the relative outputs of their units; I doubt the yield curves are such that they end up having to cripple many units because they have too many fully functional parts and not enough to fill low-end volumes.

Even if there *were* a decent percentage of fully working CPUs on on the market, you'd have to be pretty stupid to spend that amount of money on a high end motherboard to turn your CPU into a *maybe* working higher model that *may* totally destroy your data. Either that or the work you're doing is so trivially unimportant that you probably don't need a computer in the first place. Why not just buy a normal motherboard and spend the saved money on the real fully featured part.

You're showing a complete lack of understanding of, well, just about everything.

Re:Whatcouldpossiblygowrong

[LordKronos]

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.

That's what diagnostic tests are for. memtest86, prime95, etc. If you system can crank through 24+ hours of those tests, you can be reasonably certain it will perform just fine for everyday usage.

Re:Whatcouldpossiblygowrong

[Zerth]

And you apparently don't understand the mind of an overclocker; they aren't sane.

Re:Whatcouldpossiblygowrong

[Anonymous Coward]

That's why you test the core. If you have the knowledge of being able to turn on a core, you have the knowledge telling you that you should stress test it with prime95 or somesuch.
Argue this fact as much as you like, if you're the idiot who didn't check for stability it's your own damn fault.

And this information has been out for a long time and slashdot is just now finding out?

Re:Yield...

[91degrees]

Producing a chip still costs a fair amount. R&D is a substantial part of the cost as well, but fabbing a chip costs a lot more than stamping a CD. We could be talking hundreds of dollars per unit for a new process and a large enough chip.

Re:Yield...

[AlXtreme]

And you underestimate the profit product differentiation can generate.

If you have $300 to spend and you can choose between two products, one for $100 and one for $500. Which will you choose?

Now if I take that $500 product and turn it into a third product, $300 and slightly tweaked to perform less than the $500 product. Which will you choose?

You and I might take the $100 product and pocket the rest, but many buyers will go for the $300 one. As long as manufacturing costs are low it's more profitable to have a range of prices.

Re:Kernel tricks to take advantage of it?

[Pharmboy]

This reminds me of "processor affinity" or "affinity mask", whereby you assign software to a particular processor or core. If you want to setup your software so that only less cpu intensive software (cooler) runs on the questionable core, you can do this in Windows 7, and likely for at least some software in Linux (I'm really not sure here), then yes, in theory, you could do this so only Word runs on core #3.

But please remember the wisdom of Yogi Berra when trying to apply a theory like this: "In theory there is no difference between theory and practice. In practice there is."

In other words, your mileage *will* vary.

Re:How do they disable the cores?

[Joce640k]

In the past it's been done by a combination of BIOS and/or those tiny resistors soldered to the back of the chip.

Re:Mod up

[PitaBred]

I have no problem with the kids having fun playing games. I have a problem when they break things and return them for new hardware. That's pushing the cost of hardware up on the rest of us.

If you want to play, fine. Just make sure you take responsibility for what you break as well.

A Personal Story of Software Unlocking

[Liambp]

Some years back I bought a mid range graphics card called an ATI 9500 in anticipation of the soon to be released blockbuster called Half Life 2. A post on the internet alerted me to the fact that the 9500 actually used the same chip as the much more powerful ATI 9700 but with half of the channels disabled. Happily a simple software mod allowed me to unlock the missing four channels. I was delighted and enjoyed top drawer 9700 performance at a bargain 9500 price. Sadly the game Half life 2 was subject to delay after delay so I played other games while I waited, none of which really needed the extra graphics performance. It was more than a year later when Half Life 2 was finally released. I waited with renewed eager anticipation for the release date confident that my home brew 9700 would at last get a work out. Let us gloss over the fact that it took several further hours for me to download most of the game from Steam despite having an original disk. Eventually the game was installed and I eagerly started playing only to be surprised at the strange checker-board graphical effects. Google confirmed that these effects were not a creation of Valve but were in fact a sign of faulty cores on my pseudo 9700. Removing the softmod downgraded me to a vanilla 9500 and allowed me to play the game as it was intended.

Moral of the story: Sometimes manufacturers disable cores for a reason.