I'll bet it's a yield + dont-want-a-lawsuit combo

why lawsuit?

Apple gets sued for things all the time. I think there's a whole class action system set up for it.

"iPhone owners get $92 payouts from Apple in phone-throttling settlement"

https://arstechnica.com/tech-policy/2024/01/iphone-owners-ge...

etc...

"Some iPhone users eligible for $349 in lawsuit settlement payout over audio issues"

"Apple Lawsuit: M1 MacBook Pro and Air Have Display Hardware Defects, Causes Screens to Crack"

"AppleCare Class Action: Apple Agrees to $95 Million Settlement for iPhone, iPad Users Given ‘Remanufactured’ Devices"

"Apple Agrees to $50 Million Settlement Over Butterfly Keyboard Complaints"

If you make a marketing claim, the government can sue you for not selling what you say you are.

This doesn’t apply to puffery claims though, which is why Apple could have said ‘the new M2, with the best number of cores ever!’ And been fine with whatever.

They probably found that the 10th one was systemically defective, and is just disabling it now vs a crap shoot which shipped products will crash or not when using theirs. Much like what they'd do with the batteries when they'd go wonky.

Or it's simply that much cheaper to yield a 9 core than a 10 from their production. Gotta stretch that profit margin even more, they don't make enough of apple users already.

theoretically, a single defect will impact overall device yield by

  fraction of area for GPU / total device area * defect density

so, if all the GPUS are 30% of the device area, with a 5% defect density, binning from 10 to 9 is going to increase total yield by 1.6%

square that for binning from 10 to 8 so 3% yield improvement there (so ~4.6% total)

if the TMSC 3nm process is up at 10-20% then this starts to get material