I think that is the job of the embedded controller, which is before the bootloader bringing up CPU. On Chromebooks, that part is open source along with the core

I think that is the job of the embedded controller, which is before the bootloader bringing up CPU. On Chromebooks, that part is open source along with the coreboot bootloader. https://chromium.googlesource.com/chromiumos/platform/ec/+/HEAD/docs/zephyr/README.md https://chromium.googlesource.com/chromiumos/platform/ec/+/H...