Hacker News Reader

Comment by MontyCarloHall | Hacker News Reader

This is done with cores/memory banks that didn’t pass QC. For example, a 6 core CPU and an 8 core CPU might have the same die as a 12 core CPU, but 6/4 cores, respectively, were defective, so they get disabled. I don’t think they’re crippling fully functional hardware.

See here: http://isca09.cs.columbia.edu/pres/09.pdf

Also here: https://www.anandtech.com/show/2721

“When AMD produces a Phenom II die if part of the L3 is bad, it gets disabled and is sold as an 800 series chip. If one of the cores is bad, it gets disabled and is sold as a 700 series chip. If everything is in working order, then we've got a 900.”

View on HN

Specifically regarding Phenom II, I have a 550 Black Edition still plugging away, serving different roles over the years, and I was able to successfully unlock and run the two locked-out cores (via a BIOS option). It's never skipped a beat at stock clock. It could be that there was an oversupply of quad-cores, or perhaps (since it was a Black Edition part marketed to overclockers) the extra cores failed when overclocked. I know I wasn't able to have both overclock and four cores, but I considered the extra cores more important, since it was already a reasonably fast chip for its day.

It's likely the latter (that it couldn't work when overclocked with all cores). The market for those is to allow overclocking, so if it can't do any overclocking with all cores AMD likely wouldn't want to sell it as a 4-core Black Edition, since it'd probably just get returned.

> ...but 6/4 cores, respectively, were defective, so they get disabled. I don’t think they’re crippling fully functional hardware.

Hmm, but what if 3 cores are defective? If that can happen(?), then it seems one extra functional core is disabled to get to an even core number.

Apple's M1 GPUs are the first where I've seen the choice between 7 and 8 cores (as opposed to 6/8 or 4/8).

> Hmm, but what if 3 cores are defective?

It gets sold as a coaster

A coaster that allows you to play Doom.

More likely, a keychain:

https://www.amazon.com/Keychain-Ryzen-Threadripper-Computer-...

https://www.amazon.com/Keychain-Intel-Core-Computer-Chain/dp...

Kind of funny that Amazon recommends it be bought with thermal paste

I imagine there is some trade off to be made between increasingly surgical disabling of components and avoiding a menagerie of franken-SKUs. Presumably the fault rate is low enough that tolerating a single GPU core drop takes care of enough imperfect parts.

Perhaps there is fault tolerance hidden elsewhere, e.g. the neural engine might have 17 physical cores and one is always disabled. Although this seems unlikely as it would probably waste more silicon than it would save.

Reply on news.ycombinator.com