Earlier quoted context omitted.
X86-64 INCLUDES all the legacy cruft of x86-32 and x86-16 and is thus 44 years old. Aarch64 in Apple chips doesn’t include A32 and is thus 11 years old. It is indeed a large age difference.
Apple was also the first vendor to ship an ARMv8-A compatible chip; I'm sure there have been reports that they heavily influenced the design of AArch64 but I can't dig them out right now.
> 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.
> 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.