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Apple could have made their own ISA, or used one of any number of other ISAs. ARM provides a couple things. First, they offer a progression. You can start out

by ip26 8y ago

Apple could have made their own ISA, or used one of any number of other ISAs. ARM provides a couple things. First, they offer a progression. You can start out with a drop-in ARM core, and as you progress you can start customizing, and then eventually you can make your own design. (Indeed, the original iPhone CPU contained an off-the-shelf ARM11 core, and the Apple A4 was an ARM-designed Cortex-A8 with some speed tweaks by Apple) Second, obviously it's a proven starting place, you know it works well. It has been debugged, and verification is established. ARM might even license out the formal verification testing, which is a big chunk of work to develop. Designing your own ISA just takes time. Third, there's an established software base and other developers writing for ARM already. BSD already ran on ARM when Apple started making their own core, and gcc/clang have supported ARM targets for years. It's a little bit like licensing USB. Yeah, you could design your own connector with new cables and protocols and electricals. Maybe it would even be better. Or maybe the dominance of USB, proven design, extensive software stack, and so on is worth something. As for providing value, as with USB, ARM will continue to develop the ISA, guide the way for the many other smaller companies, and through their inherent leadership as the sole owners of the ISA, generally keep things cohesive & interoperable.

cpeterso 8y ago
At Apple's scale, is there much financial advantage to switching from ARM to RISC V for iOS devices? Does Apple have to pay ARM any per-device royalties?
- ip26 8y ago
  That's all closely guarded, I'm not even sure if that's public knowledge or not. Worth noting, however, Apple's quarterly revenue is like $50B while ARM's is $500M- split across many customers. Apple certainly has shown a proclivity for such bravado, but I think there's no way it wouldn't be a huge setback to the business & the competitiveness of their chips, and breaking free of Intel ASAP is probably worth a lot more than any royalties they pay ARM.
  - ksec 8y ago
    >That's all closely guarded, I'm not even sure if that's public knowledge or not. Well it isn't closely guarded really. Apple has an architecture license, which is the most expensive one time cost license but pays little to no cost per chip. Since none of the ARM designs fits Apple criteria anyway and Apple are investing into design of their own. Remember Apple has an ARMv8 64bit SoC Shipping before ARM themselves even had a ARMv8 blueprint design for PreOrder. So in terms of Financial incentives, Apple has no reason to switch to any other ISA.
    - ip26 8y ago
      Yes, arch license. But do we know for a fact that there is no per-chip or per-wafer royalty? I hadn't heard.
  - metildaa 8y ago
    There are 70 million active MacOS users, and closing in on a billion iOS users. MacOS and the hardware that runs it is an afterthought for Apple, they just want to keep it somewhat alive. Redeveloping for a new ISA was feasible when it was a life or death move Apple had to make to stay up with the rapidly improving PC world. As is Apple will likely build a customized Ryzen chip with the AMD secure enclave cut out if they want to do anything for their MacOS line of products. China literally bought the full design for Ryzen for $300 million, a custom chip would be well below that cost.
    - jeffbax 8y ago
      Apple will almost certainly not switch to AMD rather than going all in on ARM, as much as I wish I had a Ryzen Mac option. Also Apple having $50B in revenue vs $500m for ARM doesn't mean they would be guaranteed to out execute the entire loosely federated ecosystem starting from scratch. It's possible I suppose, but is unlikely to be a more efficient way to allocate financial resources.
Dylan16807 8y ago
> It's a little bit like licensing USB. Yeah, you could design your own connector with new cables and protocols and electricals. Maybe it would even be better. Or maybe the dominance of USB, proven design, extensive software stack, and so on is worth something. It's a lot like that, except smaller companies get shut out entirely. This has been changing somewhat for the better, at least.

by ip26 8y ago

cpeterso 8y ago

At Apple's scale, is there much financial advantage to switching from ARM to RISC V for iOS devices? Does Apple have to pay ARM any per-device royalties?

ip26 8y ago
That's all closely guarded, I'm not even sure if that's public knowledge or not. Worth noting, however, Apple's quarterly revenue is like $50B while ARM's is $500M- split across many customers. Apple certainly has shown a proclivity for such bravado, but I think there's no way it wouldn't be a huge setback to the business & the competitiveness of their chips, and breaking free of Intel ASAP is probably worth a lot more than any royalties they pay ARM.
- ksec 8y ago
  >That's all closely guarded, I'm not even sure if that's public knowledge or not. Well it isn't closely guarded really. Apple has an architecture license, which is the most expensive one time cost license but pays little to no cost per chip. Since none of the ARM designs fits Apple criteria anyway and Apple are investing into design of their own. Remember Apple has an ARMv8 64bit SoC Shipping before ARM themselves even had a ARMv8 blueprint design for PreOrder. So in terms of Financial incentives, Apple has no reason to switch to any other ISA.
  - ip26 8y ago
    Yes, arch license. But do we know for a fact that there is no per-chip or per-wafer royalty? I hadn't heard.
- metildaa 8y ago
  There are 70 million active MacOS users, and closing in on a billion iOS users. MacOS and the hardware that runs it is an afterthought for Apple, they just want to keep it somewhat alive. Redeveloping for a new ISA was feasible when it was a life or death move Apple had to make to stay up with the rapidly improving PC world. As is Apple will likely build a customized Ryzen chip with the AMD secure enclave cut out if they want to do anything for their MacOS line of products. China literally bought the full design for Ryzen for $300 million, a custom chip would be well below that cost.
  - jeffbax 8y ago
    Apple will almost certainly not switch to AMD rather than going all in on ARM, as much as I wish I had a Ryzen Mac option. Also Apple having $50B in revenue vs $500m for ARM doesn't mean they would be guaranteed to out execute the entire loosely federated ecosystem starting from scratch. It's possible I suppose, but is unlikely to be a more efficient way to allocate financial resources.

Dylan16807 8y ago

> It's a little bit like licensing USB. Yeah, you could design your own connector with new cables and protocols and electricals. Maybe it would even be better. Or maybe the dominance of USB, proven design, extensive software stack, and so on is worth something. It's a lot like that, except smaller companies get shut out entirely. This has been changing somewhat for the better, at least.