Apple hasn’t used off the shelf arm cores since like early 2010’s. They make their own custom CPUs. Only the ISA is ARM

so how do they differ from the A72, A53 etc?

Apple designs their own cores.

read this - https://en.wikipedia.org/wiki/ARM_architecture#ARMv8-A

Uh, is there something specific I should be looking for? I’m familiar with ARMv8-A already.

A53, A72 etc are all based on that architecture. so what is apple adding?

Apple basically makes their own thing based on the architecture as well.

their own thing. OK, got it.

really, do you have a reference?

Uh, I guess I figured this to be fairly common knowledge so the easiest thing I can point to is Wikipedia, which names their custom cores: https://en.wikipedia.org/wiki/Apple_A14. They’ve been designing these since the A6 in 2012 (“Swift”).