Values ​​returned by the E820h QuerySystemAddressMap at 4 GB + memory

Question

I just finished writing a review for a program that displays results from QuerySystemAddressMap .
I have 2 questions left:

• Having seen these - for the most unnecessary large 32-bit parameters ECX, EBXand especially the function number in EAX, I suspect that protected mode may exist for this BIOS function, is my suspicion correct?

• When the function 0000E820h BIOS executes from a real mode addresses on a computer with more than 4 GB of memory and knowing that memory above the 4 GB mark will not be addressable, will the displayed addresses and lengths remain below 4 GB?

Usually I would just give this attempt and find out on my own, but I don’t have such equipment (yet).

Answer 1

BIOS function INT 15h EAX = 0000E820h is designed to receive a full system memory card and is designed to overcome the limitations of previous interfaces that do not support memory above 4 GB. Thus, for this function, it would not make sense to report memory above 4 GB. There is no protected BIOS equivalent function mode. (Although the UEFI GetMemoryMap service provides equivalent functionality when booting through UEFI, not in the legacy BIOS boot method.)

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