Educated Guesses on Software Transitioning to macOS on ARM | Hacker News Reader

Educated Guesses on Software Transitioning to macOS on ARM

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27 pointsingve21 comments

Is it possible that Apple could add the ARM cpu to be a co-processor alongside x86? Macbook Pro 16 then has an additional powerful processor that devs can target while remaining compatible with x86. Allows a 4-5 year cycle until x86 gets dropped completely. Perhaps overly complicated and expensive to do this? I can see small/light machines (Macbook/Macbook Air) would shift to ARM only.

The T2 inside MacBook Pros is basically an A10. So it certainly isn't too expensive to do.

But it certainly is an additional complexity from software perspective.

And what about the other way? x86 as co-processor alongside the ARM as the main CPU?

Isn't moving to a new instruction set only a problem with proprietary software? Open source operating systems seem to be able to be ported to new architectures almost effortlessly, some of them quite old or obscure. It's true that some programs require modification to be able to run on new platforms, but the cost of doing that is minimal compared to the cost of "porting" binary software to new architectures, which is that of simply rewriting it from scratch. Why is everyone talking about emulation and coprocessors when the real issue is basically just a matter of source code availability?

I would love to see a provisional x86 compatibility layer baked into the silicon itself.

considering that the latest OSX is x86-64 and AVX2 only, that stuff is patented for decades to come, and its pretty much absolutely 100% Guaranteed that Intel/AMD will not give Apple a license, for any amount of money Apple would be willing to pay.

x86-64 core patents expire in 2023.

Yes, but extension instructions OSX relies on are much newer than that.

Intel has been very clear in the past they'd not let such a thing happen: https://newsroom.intel.com/editorials/x86-approaching-40-sti...

They better have an emulator to run Intel Mac apps.

They will probably not need that. Most apps should be able to be recompiled for Arm with no changes. Only a small number of apps (some audio pipeline apps for instance) are written so close to the metal that the processor change will require more work.

But there are lots of apps that aren't actively maintained, and so will never get recompiled, even if they could be. And even the ones that are actively maintained might not be ready and recompiled on day 1. Emulation would go a long way to make the transition less painful.

Bitcode[1] would’ve been a good way to handle that, if Apple had ever supported it for Mac apps in addition to their other platforms.

1. https://thenextweb.com/apple/2015/06/17/apples-biggest-devel...

I don’t see how that helps apps not in the App Store, as bitcode need to changed to a platform specific type .... unless this was done on the fly on the host platform.

Apart from a return of the dreaded Win-style endless installer progress bar surely doing it on the host, once, wouldn't be a problem. The "issue" would be squaring the result with notarization and bundle integrity, but that solves itself since it means Apple is already sitting on the (in this case bitcode) app whether it's in store or not.

But they'd probably use it as an incentive to drive stuff further towards the app store.

The bitcode is basically just LLVM IR, is it not? And that encodes plenty of platform-specific behaviours. Though with both being little-endian and both LP64 maybe there's less of an issue there?

https://lists.llvm.org/pipermail/llvm-dev/2011-October/04372... is still my go-to pointer for the portability of LLVM IR (and bitcode); I don't know how Apple have dealt with the instability between LLVM releases of bitcode, but there's certainly plenty of potentially shortcomings if you want to compile for a different architecture.

Apple is not Microsoft, if you don’t maintain your software you’re left behind.

It's not a problem for devs so much as users. If I'm not maintaining my software it's probably because I can't afford it, but the people that use it still want it installed.

I agree with the sentiment, but I feel as though 75% of the unmaintained stuff already got killed in Catalina.

They've done this before, and that's exactly what they did.

Yes, Rosetta. It allowed powerpc binaries to run under x86 (at least for a few releases until they killed it off).

https://en.wikipedia.org/wiki/Rosetta_(software)

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