[0zymandiass]

Ah. Yeah.

The motherboard just loads BIOS/UEFI into a predefined memory address and then starts the CPU

This is a pretty good explanation https://manybutfinite.com/post/how-computers-boot-up/

> In a multi-processor or multi-core system one CPU is dynamically chosen to be the bootstrap processor (BSP) that runs all of the BIOS and kernel initialization code

These days, the "bootstrap processor" is a separate core that your OS can't see. On Intel it's the IME (running Minix) and on AMD it's the PSP (ARM TrustZone)