Dissecting the Apple Silicon Mac Boot Process: From Boot ROM to Userspace

This article delves into the boot process of an Apple Silicon Mac. Starting from the Boot ROM, it traces the sequence through the Low-Level Bootloader (LLB) and iBoot, kernel startup, system clock adjustments, and finally, the unlocking of the data volume to enter userspace. Using a Mac mini M4 Pro log as an example, the article details each phase, highlighting the lower log frequency and kernel-centric entries before data volume unlock, contrasting with the significantly higher frequency and reduced kernel contribution afterwards. This process reveals insights into Apple Silicon Mac's security mechanisms and boot efficiency.