I recently got into discussion with a colleague about the MikroTik firmware. I realized that I know very few about the firmware. So far I had usually upgraded the firmware after a RouterOS upgrade. But..what are the functions implemented in the firmware? Is it just a boot environment to boot and test the hardware before the RouterOS takes over (like the Cisco's boot loader, or the BIOS)... and what happens after the boot process has finishes, how does the RouterOS interact with the firmware?
A quick search on the Internet revealed that there are not many sources which could answer the above questions. I would appreciate if the colleagues in the forum could provide more insight and probably sources about the MikroTik firmware.

For my understanding it's the bootloader (think BIOS+GRUB, uboot, redboot etc.) It might even contain some board-specific configuration (GPIO, CPU-freq, Memory addresses etc).

Thank you for clarifying this.
Are there any references who describe the firmware features in greater details?

Regards,
Boyan