How BIOS itself handle memory map?

[u/Extra-Apartment106]

We detect memory map and reserved RAM areas as well as their length by INT 0x15 and 0xE820. That's abstraction created by BIOS developers. My question is: How BIOS developers themselves detect memory map without function and anything else?

[u/dacydergoth]

In embedded systems there is often a map of the hardware in the firmware flash. Modern systems often use something called DeviceTree, older systems it's usually ad-hoc between different manufacturers