Tom, although I've not personally delved into unlocking processor cores, the
rationale is similar to that for overclocking processors (and video cards).
The manufacturer doesn't make different processor for each of the models
that they sell. Instead, they have a much more limited range of
manufactured products and go about hobbling these to get a range of less
expensive products. Depending on how mature and well honed their
manufacturing of this product is, they may or may not need to do selective
binning of what comes off the foundry line for what is destined to become
the lower end products. In other words, earlier on, chips that have defects
or problems that won't allow them to be used at their full capacity are
weeded out and sold as lesser products, but later, the selection becomes
more arbitrary and the potential for full functioning is more likely in the
hobbled product. MB manufacturers have been doing more to cater to the
enthusiasts who like to experiment with overclocking and unlocking cores by
adding things to the BIOS to make this easier, as MSI has done with their
"unlock core" feature.
Your X2 7850 BE is actually a quad core processor that has two cores
disabled. You don't have to do anything special to run it as intended.
Unlocking cores is strickly experimental, and it may or may not work out for
your particular processor. Even if you successfully unlock the cores and
find them operational, you may need to do a fair amount of tweaking and
testing to find a clock speed and voltage for keeping this now quad core CPU
stable. You'll probably have to browse some enthusiasts' hardware forums to
find the details on what BIOS settings offer the best chance of success
(i.e., 24/7 stable operation).
The Black Edition also has an unlocked multiplier, which appeals to the
overclocker. Unfortunately, it already comes with a very high clock speed,
which means that there probably is little head room for further clock
speeds; however, the ability to set your own multiplier might be an advatage
if you unlock the cores and find that you need a lower clock speed to keep
the whole thing stable. (The unlocked multiplier means that you can manage
the CPU's clock speed without resorting to changes in the motherboard's bus
speed.)
Hopefully, this offers some answers to your questions. 1) Your CPU will run
fine as a dual core processor at its stated speed of 2.8 GHz with a minimum
of changes to the BIOS, 2) Unlocking cores is not supported by the
manufacturer of the CPU (or video card); so, finding a way around this (if
it is possible) varies from product to product, though MSI offers to make
this easy for some of the AMD CPUs, 3) dead cores are locked, but whether
you can find a way to unlock them depends on the product (obviously, AMD
CPUs offer some possibilities for trying -- I've not heard of unlocking
cores in Intel products, though), 4) Since these products were not sold with
the idea that the disabled cores would be put online, it is up to you to do
the needed testing to determine whether this is viable for your particular
CPU (i.e., you'll have to do the stress testing to see if the unlocked cores
cause problems).
I hope this is helpful. As I said, I've not actually practiced unlocking
cores, though I frequently use overclocked processors.
John Sproule
------------ Original Message Below -------------
Date: Fri, 17 Dec 2010 20:02:49 -0500
From: Tom Waddell <[log in to unmask]>
Subject: Unlocking CPU cores
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?
PCBUILD's List Owners:
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Mark Rode<[log in to unmask]>
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