The choice and design of the ISA is extremely important,
it's hard to argue that the ARM ISA has no impact on M1&M2 performance.
But the ISA choice is obviously not enough to explain the whole performance of the M1&M2.
Likewise, the manufacturing process cannot fully explain the performance of the M1&M2.
The Apple microarchitecture is by far the most performant and efficient of all high-end superscalar CPU.
But be careful with simplistic explanations, the microarchitecture is always constrained by the ISA/architecture, and the x86 ISA has some flaws that can affect the microarchitecture (least on the power consumption).
Mike Clark, the architect of Zen says in [1] literally that ISA doesn’t matter and that it’s all about the microarchitecture.
Quote: “Although I've worked on x86 obviously for 28 years, it's just an ISA, and you can build a low-power design or a high-performance out any ISA. I mean, ISA does matter, but it's not the main component - you can change the ISA if you need some special instructions to do stuff, but really the microarchitecture is in a lot of ways independent of the ISA. There are some interesting quirks in the different ISAs, but at the end of the day, it's really about microarchitecture.”
In the end, ISA is such a small part that impacts the design of a modern high performance CPU that it is almost negligible. It is physically impacting only the decode unit, but the decode unit is only a few percent of die area. Feel free to listen to the whole interview to get a feeling.
- Variable instruction sizes make the front-end more complex and limits the decoding width;
- Delayslot makes superscalar front-end more complex;
- Page size limits VIPT L1 cache size;
- Dedicated SIMD/FP architectural registers allow dedicated SIMD/FP physical register files;
...
The choice and design of the ISA is extremely important, it's hard to argue that the ARM ISA has no impact on M1&M2 performance.
But the ISA choice is obviously not enough to explain the whole performance of the M1&M2. Likewise, the manufacturing process cannot fully explain the performance of the M1&M2.
The Apple microarchitecture is by far the most performant and efficient of all high-end superscalar CPU.
But be careful with simplistic explanations, the microarchitecture is always constrained by the ISA/architecture, and the x86 ISA has some flaws that can affect the microarchitecture (least on the power consumption).