Apple's claim is that they designed it themselves. https://en.wikipedia.org/wiki/Talk:Apple_M1#[dubious_%E2%80%...
Also, if you read Hector Martin's tweets (he's doing the reverse-engineering), Apple replacing the actual logic while maintaining the "API" of sorts is not unheard of. It's what they do with ARM themselves - using their own ARM designs instead of the stock Cortex ones while maintaining ARM compatibility.*
*Thus, Apple has a right to the name "Apple Silicon" because the chip is designed by Apple, and just happens to be ARM-compatible. Other chips from almost everyone else use stock ARM designs from ARM themselves. Otherwise, we might as well call AMD an "Intel design" because its x86 by the same logic.
They did this with ADB, early PowerPC systems contained a controller chip that has the same API that was implemented in software in the 6502 IOP coprocessor in the IIfx/Q900/Q950.
https://twitter.com/stuntpants/status/1346470705446092811
> arm64 is the Apple ISA, it was designed to enable Apple’s microarchitecture plans. There’s a reason Apple’s first 64 bit core (Cyclone) was years ahead of everyone else, and it isn’t just caches
> Arm64 didn’t appear out of nowhere, Apple contracted ARM to design a new ISA for its purposes. When Apple began selling iPhones containing arm64 chips, ARM hadn’t even finished their own core design to license to others.
> ARM designed a standard that serves its clients and gets feedback from them on ISA evolution. In 2010 few cared about a 64-bit ARM core. Samsung & Qualcomm, the biggest mobile vendors, were certainly caught unaware by it when Apple shipped in 2013.
> > Samsung was the fab, but at that point they were already completely out of the design part. They likely found out that it was a 64 bit core from the diagnostics output. SEC and QCOM were aware of arm64 by then, but they hadn’t anticipated it entering the mobile market that soon.
> Apple planned to go super-wide with low clocks, highly OoO, highly speculative. They needed an ISA to enable that, which ARM provided.
> M1 performance is not so because of the ARM ISA, the ARM ISA is so because of Apple core performance plans a decade ago.
> > ARMv8 is not arm64 (AArch64). The advantages over arm (AArch32) are huge. Arm is a nightmare of dependencies, almost every instruction can affect flow control, and must be executed and then dumped if its precondition is not met. Arm64 is made for reordering.
This is such an interesting counterpoint to the occasional “Just ship it” screed (just one yesterday I think?) we see on HN.
I have to say, I find this long form delivery of tech to be enlightening. That kind of foresight has to mean some level of technical saaviness at high decision making levels. Whereas many of us are caught at companies with short sighted/tech naive leadership who clamor to just ship it so we can start making money and recoup the money we’re losing on these expensive tech type developers.
Therefore, there is no basis for saying that AArch64 is a cleaned-up MIPS-like ISA. Only RISC-V is a MIPS-like ISA.
One of the few features of AArch64 that can be said to be similar to MIPS was its main mistake.
In the initial ARMv8.0 version, the only means provided for implementing atomic operations was a load-and-reserve/store-conditional instruction pair.
This kind of instruction has been popularized by MIPS II, but it had not been invented by MIPS, but by Jensen et al. (November 1987), for the S-1 AAP multiprocessor.
While this instruction pair allows the implementation of lock-free/wait-free data structures, it can be extremely inefficient for implementing locks in systems with many cores (because progress is not guaranteed), so in the ARMv8.1 version the initial mistake has been corrected, by adding atomic instructions of the type fetch-and-op, besides the MIPS-like LL/SC pair.
It is a good feature, which can reduce substantially the number of instructions that must be implemented, because many single-operand operations are just special cases of double-operand operations with one null operand.
This is why it was used in many early computers, which had to be simple due to the limitations of their technology, and then it was used again in most RISC CPUs, which have been simplified intentionally (and not only in MIPS; among the more successful RISC ISAs also IBM POWER has it; only 32-bit ARM does not have it, due to its unusually low number of general-purpose registers, in comparison with the other RISC ISAs).
My StrongArm powered RiscPC was amazing for the time. It was strange that the contemporaneous Newton was powered by the same (and in some ways better) processor.
The connection between ARM processors being used in desktop and mobile devices is in its early DNA.
1. https://www.anandtech.com/show/16226/apple-silicon-m1-a14-de...
IMO the Kyro/820 wasn't a major failure, it turned out a lot better than the 810 which had A53/A57 cores.
And then they decided they needed a mobile CPU team again and bought Nuvia for ~US$1 Billion.
As for Apple, they've designed their own cores since the Apple A6 which used the Swift core. If you go to the Wikipedia page, you can actually see the names of their core designs, which they improve every year. For the M1 and A14, they use Firestorm High-Performance Cores and Icestorm Efficiency Cores. The A15 uses Avalanche and Blizzard. If you visit AnandTech, they have deep-dives on the technical details of many of Apple's core designs and how they differ from other core designs including stock ARM.
The Apple A5 and earlier were stock ARM cores, the last one they used being Cortex A9.
For this reason, Apple is about as much an ARM chip as AMD is an Intel chip. Technically compatible, implementation almost completely different. It's also why Apple calls it "Apple Silicon" and it is not just marketing, but actually justified just as much as AMD not calling their chips Intel derivatives.
Before that, they had Scorpion and Krait, which were both quite successful 32 bit ARM compatible cores at the time.
Kryo started as an attempt to quickly launch a custom 64 bit ARM core and the attempt failed badly enough that Qualcomm abandoned designing their own cores and turned to licensing semi-custom cores from ARM instead.
https://en.wikipedia.org/wiki/Apple_silicon
https://www.anandtech.com/show/7335/the-iphone-5s-review/2
> NVIDIA and Samsung, up to this point, have gone the processor license route. They take ARM designed cores (e.g. Cortex A9, Cortex A15, Cortex A7) and integrate them into custom SoCs. In NVIDIA’s case the CPU cores are paired with NVIDIA’s own GPU, while Samsung licenses GPU designs from ARM and Imagination Technologies. Apple previously leveraged its ARM processor license as well. Until last year’s A6 SoC, all Apple SoCs leveraged CPU cores designed by and licensed from ARM.
> With the A6 SoC however, Apple joined the ranks of Qualcomm with leveraging an ARM architecture license. At the heart of the A6 were a pair of Apple designed CPU cores that implemented the ARMv7-A ISA. I came to know these cores by their leaked codename: Swift.
Yes, Apple has been designing and using non-reference cores since the A6 era, and were one of the first to the table with ARMv8 (apple engineers claim it was designed for them under contract to their specifications, but this part is difficult to verify with anything more than citations from individual engineers).
I expect that Apple has said as much in their presentations somewhere, but if you're that keen on finding such an incredibly specific attribution, then knock yourself out. It'll be in an apple conference somewhere, like WWDC. They probably have said "apple-designed silicon" or "custom core" at some point, and that would be your citation - but they also sell products, not hardware, and they don't extensively talk about their architectures since they're not really the product, so you probably won't find a deep-dive like Anandtech from Apple directly where they say "we have 8-wide decode, 16-deep pipeline... etc" sorts of things.