It seems to me that if Apple felt that Nvidia would limit them, they could have outbid them for ARM! So I think you are correct.
Offer customers iOS apps and games on the next MacBook as a straight swap for Boot Camp and Parallels. Once they’ve moved everyone over to their own chips and brought back Rosetta and U/Bs they’re essentially free to replace whatever they like at the architecture level.
In their reveal I noticed that they only mentioned ARM binaries running in virtual environments. It makes sense if you don’t want to commit to supporting GNU tools natively on your devices (as it would mean sticking with an established ISA)
Apple is large enough that if they want to break from ARM in the future they can do so by forking an LLVM backend. That's not a large job if it's a very small change, but once it's been done once they have plenty of resources to provide ongoing support (like they do for webkit).
The dividends of doing so are potentially massive. Given that they've been able to make really large gains with the A series chips to date on mobile (not least because they've been able to offload tasks to dedicated co-processors that general-purpose ARM cores don't ship with), the rewards for having chips that are a generation ahead of other like-for-like computers will outweigh the cost of maintaining the software.
I guess they have some ISA flexibility (which is remarkable). But not much; each transition was still a very special set of circumstances and a huge hurdle, I'm sure.
As in, most of the work occurs in the low-level parts of the Operating system. After that the OS should abstract the differences away from User-space.
First of all: there's lots of software that's not the OS. The OS is the easy bit: everything else: grindy, grindy horrorstory. A lot of that code will be third-party. And if you think, "hey, we'll just recompile!", and you can actually get them to too - well, good luck, but performance will be abysmal in many cases. Lots and lots of libraries have hand-tuned code for specific architectures. Anything with vectorization - despite compilers being much better than they used to be - may see huge bog downs without hand tuning. That's not just speculation; you can look at software that's gets the vectorization treatment or was ported to arm from x86 poorly - perfomance falls off a cliff.
Then there's the JITs and interpreters, of which there are quite a few, and they're often hyper-tuned to the ISA's they run on. Also, they can't afford to run something like LLVM on every bit of output; that's way too slow. So even non-vectorized code suffers (you can look at some of the .net core ARM developments to get a feel for this, but the same goes for JS/Java etc). Webbrowsers are hyper-tuned. regexengines, packet filters, etc etc etc
Not to mention: just getting a compiler like LLVM to support a new ISA as optimally as x86 or ARM isn't a small feat.
Finally: at least at this point, until our AI overloads render that redundant - all this work takes expertise, but that expertise takes training, which isn't that easy on an ISA without hardware. That's why Apple's current transition is so easy: they already have the hardware; and the trained experts some with over a decade of experience on that ISA!. But if they really want to go their own route... well, that's tricky, because what are all those engineers going to play around on to learn how it works; what's fast, and what's bad?
All in all, it's no coincidence transitions like this take a long time, and that's for simple (aka well-prepared) transitions like the one's Apple's doing now. Saying they have ISA "flexibility", like they're somehow interchangeable is completely missing the point on how tricky on those details are, and how much they're going to matter on how achievable such a transition is. Apple doesn't have general ISA flexibility, it has a costly route from specifically x86 to specifically ARM, and nothing else.
The vast majority of the code written for any given computer or smartphone doesn't have this level of sophistication and optimization though. I'd wager that for most code just changing the build target will indeed mostly just work.
It won't be painless but modern code tends to be so high level and abstracted (especially on smartphones) than the underlying ISA matters a lot less than in the past.
This isn't a question of precise instruction timing, it's a question of compilers being pretty bad at leveraging SIMD in general, even in 2020. Also, while I'm sure lots of projects have hand-tuned assembly, even higher level stuff like intrinsics help a lot, and need manual porting.
Also - why would Apple massively up and change uArchs? Even if they did decide to turn Apple Silicon into not-ARM, I'd wager it would look a lot more like ARM than for example, x86 does.
Also likely the small tweaks they will want from time to time should be "easy" to follow internally, if you can orchestrate everything from top to bottom and back.
Not to mention starting a JV has nothing to do with perpetual IP access. You will still have to pay for it.
I obviously don't know that for sure but the idea that Apple would stake their future on something they don't have a legal ironclad position seems unlikely.
Just because Apple and nVidia has bad relationship at the moment regarding their GPUs is probably orthogonal to what they'll do with this new branch of nVidia, that is ARM.
True about frenemies the entire time that Apple was suing Samsung, it was using Samsung to manufacture many of its components.
Since they're not branding it as ARM in any way, shape, or form, and they have a perpetual architectural license to the ISA, I suspect they could do pretty much what they please - as long as they don't call it ARM. Which they don't.
Even if not, then yes, I would imagine that a behemoth of IP design like Apple would probably have considered IP rights during that design...
Yea, they got fucked by Nvidia business practices multiple times. There's a saying about shame on you, shame on me, etc. Unless the entire Nvidia business unit also gets replaced in the same transaction, it doesn't matter how much of a faux separation of concerns they want to market.