The amount of work that went into putting this document together can not be understated; it requires both a deep understanding of the ARM architecture and its diagnostics efforts, as well as hours of testing, technical document and patent reading, and community discussion. The offered documentation is a way to collect already-known, existing information and reverse-engineering research results on the M1 chip, but also adds to these efforts with Handley’s own experiments (an exploration of Apple’s efforts on branch prediction and hardware and logic mitigations for Spectre-like exploits is also included — it’s an interesting read).
Apple’s M1 chip shocked the tech world because of its incredible IPC and power-to-performance ratio, shifting the spotlight from x86 as the de-facto high-performance architecture. However, as impressive as Apple’s silicon efforts are, the company’s walled-garden approach means that anyone who wants to take advantage of the M1 hardware has to either go through Apple’s own operating system, MacOS, or go the reverse-engineering route of optimizing another software stack to use on the Apple silicon. Nevertheless, many engineers have taken this task to heart and even recently managed to run Linux fully on the M1 chip.
While this isn’t a definitive edition, Handley’s efforts can now become a community-driven M1-geared Bible. Most of the work done here could also help open the doors to reverse-engineering the expectedly more powerful Apple M2. It’s interesting to see the amount of work that goes into bringing a closed-system, purpose-built hardware platform into the more welcoming arms of open-source.