Logic behind disabled cores?

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Rishi87

Broken In
Hello guys. I recently read reviews of some triple and dual core processors from AMD. some of them (Mostly triple core processors) are quad cores with one or two cores disabled.

So, my question is why do they disable those cores? Just to avoid an architecture change or is it a part of manufacturing process to use the faulty chips?
 
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pimpom

Cyborg Agent
I'm not 100% sure, but I believe they're making good use of imperfect cores, that is, quad cores in which one core is defective.

Actually, this is a clever idea. Many CPUs (whether single core or multiple core) are made at the same time from a single silicon wafer, but manufacturing CPUs is such a difficult process that a large percentage comes out defective. Some of the defective units can be repaired with laser trimmers, but some have to be rejected.

With multiple cores, one core may be defective while the others are perfectly OK. Marketing those with the defective core disabled is a good idea.
 
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otpsurvive

Broken In
And certain batches of those CPUs with one or two cores found defective aren’t actually defective. Sometimes due to higher demand for these processors, those cores are deliberately disabled and sold at a lower price. If you’re one of those lucky few who manages to get hold of this batch of CPUs then you can unlock the other cores and get more bang for your buck. Although, you may void warranty in doing so, most such procs work just fine.
 
infra_red_dude

infra_red_dude

Wire muncher!
1) To save on fabrication costs. The company doesn't need to send more than 1 mask to the fab (which is exorbitantly costly).
2) To make use of defective dies (one core maybe defective, so instead of throwing away the whole die, they are marketed as a lower end version).
 
asingh

asingh

Aspiring Novelist
otpsurvive said:
And certain batches of those CPUs with one or two cores found defective aren’t actually defective. Sometimes due to higher demand for these processors, those cores are deliberately disabled and sold at a lower price. If you’re one of those lucky few who manages to get hold of this batch of CPUs then you can unlock the other cores and get more bang for your buck. Although, you may void warranty in doing so, most such procs work just fine.
Click to expand...

So if someone unlocks a defective one..what happens..??
 
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pimpom

Cyborg Agent
infra_red_dude said:
If its the 1) case from my post then you are in for trouble as you will haf stability issues.

If the reason for disabling was 2) then you haf a core for free! :)
Click to expand...
Hey, IRD: aren't you a bit mixed up about your own post? :) You interchanged 1) and 2) in this post.
 
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