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:
                      Bob Wright<[log in to unmask]>
                        Mark Rode<[log in to unmask]>