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(multiboot.info)Notes on PC

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Notes on PC
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   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 (Note: 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 Note: 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.