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Unlocking dual core CPU

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December 18, 2010 4:49:57 PM

I am building a new computer to hook up to our HDTV, primarily to watch and record on-line programs through Windows Media Center. I have an AMD Athlon X2 7850 Black Edition AM2 CPU. I had this CPU in an MSI MB that didn't work out. While setting up the BIOS I noticed an "Unlock Core" function. I have not seen this before and do not know anything about why multi-core CPU's need to be unlocked. I assumed if the CPU has multiple cores, all would be working. Then I discovered the unlock function.

Questions:

1 - Have ordered a Gigabyte MB (due in 12/21) to replace the MSI and want to make sure I set up the CPU correctly.
2 - THINK I have read here that multi core CPU's can only be unlocked if the CPU supports it. Correct me if I am wrong.
3 - THINK I have read here that dead cores will be locked and can not be unlocked, correct?
4 - Also, cores that work but are not fully functioning can be unlocked but will cause problems, right?

Have worked as an electronics tech for 15 years and have been building computers a long time (10 in 15 years for family) but mostly just put them together "AS-IS". Am retired now and want to learn the finer points of computer building.

PC Specs

MB - Gigabyte MA785GM-US2H AMD785G Socket AM2+ MB
CPU - AMD Athlon X2 7850 Black Edition AM2 OEM CPU
Mem - Corsair 4096MB PC6400 DDR2 800MHz (2x2048MB) DHX
Cooler - Thermaltake CPU Cooler for AMD Opteron & Athlon 64
PS - Corsair VX450W 450W Power Supply
DVD - Plextor 24X DVDRW SATA w/Lightscribe
OS - Win 7 Pro 64 bit
HD - Seagate Barracuda 7200.11 500GB 7200 RPM
TV Card - Hauppague 1600

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a c 199 à CPUs
December 18, 2010 5:10:49 PM

The unlock cores function comes from how AMD bins their chips, all Athlon II and Phenom II chips are made as Phenom II X4s, if if comes out with a bad core or two it gets the cores disabled to make it a Phenom II X3 or X2, if it comes out with some bad L3 cache it gets turned into an Athlon II.

Your CPU does not allow core unlocking because it is only a dual core CPU on all levels so that feature will not work for you.

There are a few reasons they might lock cores, they may not be able to run the same speed as the others at the same voltage so that core would cause the whole chip to get binned lower unless they lock it; the core may be critically damaged, like something went wrong in the process and its totally bad, or it may be more leaky and create a lot more heat than the other ones so they lock it to keep the chip cooler. On the Athlon II's and Phenom II's less than 40% successfully unlock anything.
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a b à CPUs
December 18, 2010 5:24:30 PM

You're fairly on the ball so far.

This unlocking thing is just about taking advantage of AMD's binning process. Sometimes, chips made for higher grade series (like x4) don't work out to spec, so they tune it down to a spec where it works, locking features and such in the process. Other times, its just a matter of wanting to 'spread' the same design out among multiple series of processors by tweaking their specs right out of the factory.

Of course, as consequence, unlocking is a gamble. Sometimes, it just doesn't have the extra core(s), if it does, they won't be stable and they'll cause the chip to heat up a lot. Sometimes, they'll unlock perfectly fine and you're suddenly working with a chip that's worth more than $50 more than what you payed.

The 'quality' of the unlock can vary by motherboard and chip, but the 785Gs with the feature that I know of do a good job when the chip actually has the core(s).
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a b à CPUs
December 18, 2010 6:52:46 PM

I read that AMD actually ran out of dual core cpu's and consequently took a load of fully functional quads and disabled cores to make then dual cores instead of manufacturing a load of new duals.

This lead to a load of successful unlocks as after all the cpu's where fully functional quads to begin.

From personal experience I unlocked my PII 555 to a quad and its fully stable @3.7 but its all a gamble.

Bottom line is if you want a quad, buy a quad. :??: 
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a c 199 à CPUs
December 18, 2010 7:43:03 PM

They didnt run out of dual cores, they simply never made any. There are always bad chips on every wafer, so instead of just throwing out the ones with bad cores they turned them into dual cores.
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a b à CPUs
December 18, 2010 8:22:27 PM

I see, so maybe they ran out of faulty ones and started disabling the functional quads?.

What sort of numbers are we talking when they say faulty chips in a batch, just out of interest? :heink: 
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December 19, 2010 1:58:58 AM

Thanks for explaining unlocking cores. I had no idea what it meant. Now I know I can build a computer with a dual core processor and have no worries about setting up the CPU correctly.
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December 19, 2010 2:17:26 AM

ummm... your welcome? why did you start a thread just to thank someone?
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a b à CPUs
December 19, 2010 2:29:22 AM

Quote:
ummm... your welcome? why did you start a thread just to thank someone?

[:grahamlv:3]

+1

A lot of us are kinda at a lose for why your starting a thread for thanking someone and who your thanking for :whistle: 
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a b à CPUs
December 19, 2010 10:18:53 AM

This next topics has been merged by Mousemonkey
  • Thanks for explaining unlocking cores
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    December 19, 2010 11:04:04 AM

    OK, first, this is not downbinning, it is down coring. There is a difference. Second, I do not believe that we would be making duals out of quads.

    The process you are talking about is die harvesting, where dies with one bad core are down cored from a 4 to 3 core die. I would guess that it probably also happens from 6 to 4 as well. On the server side we do that.

    The reason I doubt it would happen on the dual side is that a dual is 50% of the core silicon space and it would be cheaper in the long haul to design a dual and manufacture a dual vs. trying to manage that by down coring a quad.

    But I am not on the client side of the house, so I don't know for sure how they do it over there.
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    December 20, 2010 8:01:25 PM

    alhanelem said:
    ummm... your welcome? why did you start a thread just to thank someone?


    To let others know the question I had posted about unlocking cores had been resolved. I have been on a few other computer web sites and this is the first one I have seen where people post a separate "resolved" posting about a previous question. I thought my posting said "Resolved" but I see it didn't. My mistake.

    Usually these resolved or thank you posting get posted under the original post, but then after awhile few people will open the original posting and won t see the thank you or problem resolved posting. Just thought this was the norm for this web site. Have to say this is the best computer web site I have found. Posts show up right away, get fast replies and the in depth articles are great.
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    December 27, 2010 4:48:42 PM

    Best answer selected by Maineman.
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