On the latest episode of the Accidental Tech Podcast they were discussing a patent related to this fancy interconnect stuff, and it sounds like not only do they need two fully functioning M1 Max's, but they also need to be adjacent on the wafer. Although I guess at least they can still use the non-defective M1 Max in any pair.

That would be an interesting approach: don't know if it's what they're doing, but if they're like 'make M1 Ultras predominantly, but then if they break you're making M1 Max with an attached bit that has to be trimmed off', that's pretty ingenious.

I think I've seen a picture of a decapped M1 Max and it had this extra part on the side that never appeared in Apple renders. It was back then when this speculation of it having multiprocessor interconnect started. It was then also confirmed by Asahi Linux people from the software side of things.

So no, they don't even bother to trim it off.

The M1 Ultra is essentially two M1 Max joined together. I suspect most of the things which can go wrong are at the M1 Max level. I'm sure a certain percentage where fusing two dies together kills one or both dies, but I suspect that's probably a manageable percentage.

This is the reason there are lower-end models of all M1 chips with some CPU and GPU cores disabled. And the M1 Ultra is just two M1 Max glued together.

> Things can go wrong at [..] the memory etc

The memory isn't on die. It's just regular lpddr5 but on package. So that's not a yield concern.

in general the lower yield ones ended up being the lesser model such as M1 Pro using the same die