You can learn a great deal from the unified log entries of a system startup, and that for an M1 Mac is even more fascinating for the insights it gives into the hardware in the M1 system-on-a-chip (SoC). These were obtained from an M1 MacBook Pro with 8 CPU cores and 8 GPU cores running macOS 11.0.1 fairly clean, and in full Secure Boot.
The iBoot firmware phase occurs before the start of logging, so the first entries are those from the kernel. For each log entry, the initial field is the system clock time in seconds.
Kernel phase
The first part of the boot sequence takes around 7 seconds, most of which is loading and initialisation of the kernel. This takes place on one of the CPU cores, here number 7, which is a ‘type 2’ core, presumably one of the four high-performance or Firestorm cores. As with Intel Macs, the first entry in the log is the standard announcement of the start of system boot. This is given with a UUID which uniquely records that event, is provided in System Information, and written into every log entry.03.392395 === system boot: AE70F6FC-3AC5-4A05-81AA-D680203A1AF9
Following that, interrupt controllers are set up, and the kernel version declared.09.939481 kernel Darwin Kernel Version 20.1.0: Sat Oct 31 00:07:10 PDT 2020; root:xnu-7195.50.7~2/RELEASE_ARM64_T8101
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