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Comment by 2bitencryption | Hacker News Reader

Question - now that Apple is shipping its own ARM silicon - is Apple beholden to the ARMv9/10/11/etc future? (edit: duh, Apple has been shipping ARM silicon long before M1, I forgot)

Does Apple now have enormous input into the ARM spec process? (Or maybe they did already, because iPhones?)

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The conditions in the agreement between arm and Apple aren't public so you can't say for sure. Historically arm hasn't allowed architecture licensees to do their own thing. You're implementing arm standard architecture (and passing the conformance test suite) or nothing. Looks like they've given Apple some special dispensation to do things differently (e.g. the custom AMX instructions that have been uncovered https://gist.github.com/dougallj/7a75a3be1ec69ca550e7c36dc75...).

For ARMv9 this potentially means they can pick and choose what they want to implement. I'm sure Apple has had plenty of input into the specification (along with other partners).

They can only implement a superset of a specification, no mix-and-match allowed.

As an exception, an ARMv8.x-A chip can have some ARMv8.x+1-A extensions, but _never_ 8.x+2-A extensions (forbidden by Arm).

You just have one ISA minor revision of wiggle room.

And yes, Arm architectures are co-designed with plenty of output from partners.

Except we have evidence that they've been implementing a subset of the specification on M1. Like VHE stuck on.

The not well kept rumor is that Apple has a much looser than architectural license due to their very close relationship with ARM, both generally since the early 90s, and that Apple contributed very heavily to early AArch64 design and it's arguably theirs as much as it is ARM's.

VHE is implemented and stuck as on indeed.

There's also the fact that only pc and sp are retained on WFI, without the other GPRs.

Those quirks only affect bare metal kernel-mode (EL2), and do not affect user-mode or virtualised machines at EL1 in any way.

ARM was founded as an Apple joint venture. Their relationship is probably special.

The fact that the current M1 already ships with an undocumented Matrix Multiplication implementation leads me to believe that Apple was one of the development partners for this new version of the spec.

https://medium.com/swlh/apples-m1-secret-coprocessor-6599492...

>All licensees are not equal however, the first few are called lead licensees and companies pay an added fee for this honor. ARM picks 2-3 lead licensees for each market segment and works closely with them.

https://semiaccurate.com/2013/08/07/a-long-look-at-how-arm-l...

Apple is one of the co-founders of the Arm holdings company all the way back then.

Even though Apple and Arm are possibly "at-arms" organizations these days (no one outside of these organizations really will know, except the lawyers, and the contractual obligations between Apple and Arm are likely locked up and highly secretive)

I'd say the other way around, that Arm is beholden to where Apple wants to take the Arm ecosystem, if only by way of showing other participants in the arm ecosystem what is possible. IE. Amazon is able to use the M1 as a gauge to how far it might be able to take its own Graviton cores.

Yeah, agreed. People assume that the power relationship between Apple and ARM is the same as between Apple and other architectural license holders, but all signs point to their relationship being very different with them being at least full partners and maybe Apple being the one dictating terms.

Apple don't use ARM's microarchitecture.

Apple designs their own chips using ARM ISA (instruction set architecture). They design completely different chips separate from ARM.

Handful of companies like Apple, Broadcom, Marvell, Intel, Qualcomm, Samsung, have bought ARM architecture license.

Apple is a co-founder of Arm. Arm partners all play a role in the design of the Arm specifications.

To be clear, Apple was a co-founder of Advanced RISC Machines Ltd (which became the current Arm Ltd), five years after the ARM (Acorn RISC Machine) architecture.

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