In reference to bit 0 of the flags
parameter in the Multiboot
information structure, if the bootloader in question uses older
BIOS interfaces, or the newest ones are not available (see
description about bit 6), then a maximum of either 15 or 63 megabytes of
memory may be reported. It is highly recommended that boot
loaders perform a thorough memory probe.
In reference to bit 1 of the flags
parameter in the Multiboot
information structure, it is recognized that determination of which
BIOS drive maps to which device driver in an operating system is
non-trivial, at best. Many kludges have been made to various operating
systems instead of solving this problem, most of them breaking under
many conditions. To encourage the use of general-purpose solutions to
this problem, there are 2 BIOS device mapping techniques
(see BIOS device mapping techniques).
In reference to bit 6 of the flags
parameter in the Multiboot
information structure, it is important to note that the data structure
used there (starting with BaseAddrLow
) is the data returned by
the INT 15h, AX=E820h -- Query System Address Map call. See See Query System Address Map, for more information. The interface here is meant to allow a
boot loader to work unmodified with any reasonable extensions of the
BIOS interface, passing along any extra data to be interpreted by
the operating system as desired.