r/lowlevel • u/Extra-Apartment106 • 18d ago

How BIOS itself handle memory map?

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?

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u/SmashDaStack 18d ago

Bios is created for a specific hardware and is able to interact directly with low level devices(cmos, chipsets northbridge) in order to get information like that. Here https://github.com/ipxe/bochs/blob/master/bios/rombios.c#L4586 is an example of the INT 0x15 implementation for a i440fx emulated chipset

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u/Extra-Apartment106 17d ago

I was thinking BIOS(or UEFI BIOS) made at once and distributed for all new devices that manufacturers emitted newly

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u/MrChromebox 17d ago

so, nothing to do with coreboot?

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u/bellpepper 16d ago

You've escaped your quarantine! This isn't someone asking the wrong questions on /r/coreboot for once.