This seems very, very unlikely to me. RISC-V is a very similar architecture to AArch64; I haven't heard a reason to expect it to have improved performance or efficiency. (Its only distinguishing feature (that I know of) is compressed instructions -- which ARM used to have (THUMB mode) before dropping support in AArch64, so presumably it doesn't help on Apple's systems with their huge caches and high memory bandwidth.)
Rather, RISC-V's primary advantage over ARM is its openness; vendors can do whatever they want with the ISA without having to pay license fees or maintain compatibility. But this doesn't affect Apple at all; they co-founded ARM, and they have a huge amount of influence over the direction of the architecture along with some sort of special license that allows them to do things other CPU vendors aren't allowed to do (https://news.ycombinator.com/item?id=29782840, https://twitter.com/stuntpants/status/1346470705446092811).
Developing an entirely new high-end CPU mircoarchitecture takes many years and many billions of dollars. It's not something Apple's going to do unless they have a very, very good reason -- and RISC-V being really cool is unfortunately not a good enough reason.
I agree, it’s seems unlikely they will have another transition as they now control their own destiny.
The fact that Arm64 doesn’t have compressed instructions is obviously a very deliberate choice, thus I can’t agree with the notion that RISC-V compressed instructions could be a potential “advantage” over Arm64. Their absence is a massive advantage in many ways that I have explained over and over on HN and it’s the single biggest stupidity in RISC-V for high-end perf (not microcontrollers).
ARM instruction set licensing is a drag, an inefficiency.
ARMv8 is a nice ISA, and the work that architects do is critical, and it's not easy to develop a precise, clean, extensible, and relatively bug free ISA. But there is relatively little real innovation in it. It's a pretty conventional RISC, warmed over for the modern era. In fact no ISA has any real magic, that's all in the silicon.
There's certainly not hundreds of millions of dollars per year worth. That money is only paid because of the proprietary lock-in and ecosystem around the ISA, which is similar to the proprietary software model, so at some point it would be easy to imagine large chunks of the industry deciding to break away and go to something more open.
It may not inevitably displace ARM entirely, and ARM Ltd might change their ways or open their ISA to prevent it. But it could easily happen too, in the next decade or so.
As you know Arm makes most of its money selling actual designs, not the ISA. I suspect Apple pays very small fees which are not material in the context of the Mac.
For that it probably gets access to the full range of Arm IP, including for example the IP associated with big.LITTLE - and there are likely to be others.
There are two areas where RISC-V, for example, does have present a clear advantage for firms: where firms want to innovate on top on an ISA (eg Tenstorrent) or who want to shave cents off their BOM (eg WD).
ARM makes most of its money in royalties, not licensing. Under royalties, how much comes from chips that use their designs and how much from ones that don't, I don't know. Do they make that data available?
> I suspect Apple pays very small fees which are not material in the context of the Mac.
There were at a minimum 1.5 billion A series based CPUs sold last year - possibly a lot more. Arm’s total royalty sales were $1.5bn. I think we can safely say that the fees Apple pays - with its architecture license - are not material in the context of the Mac.
> There were at a minimum 1.5 billion A series based CPUs sold last year - possibly a lot more. Arm’s total royalty sales were $1.5bn. I think we can safely say that the fees Apple pays - with its architecture license - are not material in the context of the Mac.
I don't see how that follows. You don't know what their royalty arrangement is. It's probably related to the value of the chip sold. If they sell 20 million macs a year and pay ARM 2 bucks a chip that's 40 million every year. If macs have a gross profit of a couple of billion that's not insignificant. Could be 5% of that. Not to mention several hundred million a year for iphones. Lot of money to pay to be locked into a proprietary ISA when you almost entirely support your own ecosystem, compilers, OSes, etc anyway.
Apple’s net margin is around 25% so that’s around $300 per Mac sold so with your $2 it’s about 2/3% for which it probably gets access to all of Arm’s IP (eg big.LITTLE) as well as use of an ISA that Apple has long experience using and almost certainly helped to shape. As I said not material in this context.
Oh and they are clearly not locked in as they have just changed the ISA for Macs anyway.
This certainly applies to random manufacturers, but not necessarily Apple. Do they pay royalties to ARM at all? And of course, they could create any ISA extension, if they wanted. But currently they seem to be heading more into the direction of creating additional compute units (like the neural processors) rather than adding new instructions to the CPUs.
> This certainly applies to random manufacturers, but not necessarily Apple. Do they pay royalties to ARM at all?
I don't know if there are any public details about license and royalty structure for Apple, but this is ARM Ltd's core business and it's how they make their money. So, probably.
> And of course, they could create any ISA extension, if they wanted.
I'm not sure about that. I think licensees are bound by certain requirements to implement the architecture faithfully. Now Apple obviously has a huge sway and could lobby ARM to make changes it wants. But it does not necessarily have final control of that either.
> But currently they seem to be heading more into the direction of creating additional compute units (like the neural processors) rather than adding new instructions to the CPUs.
As Apple is a co-founder of ARM and holds and architectural license, I think the chances are high, that they neither pay any or significant royalties and have a lot of freedom. As could be seen in the special switch making the memory semantics of the Apple Silicon match that of x86, making the job of Rosetta easier.
Apple has invested billions to make a full transition to ARM.
I'd think that they would have to spend at least $50 billion or more to redesign all the Apple Silicon from the iPhone to the Mac Pro, rewrite 5 or 6 operating systems, and beg developers to recompile their apps.
It'd be a nightmare.
I think Apple will stay on ARM for at least 20 years...
Why just 20 years? This direction gives full control of a silicon roadmap. They can make it whatever they want or need. My guess is they have a more specific roadmap than even Intel or AMD at this point, as they're not commodity processors, but now engineered for a very specific purpose.
