Category: DOS kernel
Flags: callout or callback (usually hooked rather than called), Undocumented function
INT 2F - DOS 5+ - DOS SUPERVISOR "REBOOT PANEL" - ADJUST MEMORY SIZE
AX = 4A06h
DX = segment following last byte of conventional memory
Return: DX = segment following last byte of memory available for use by DOS
Desc: used to override the default memory size when booting diskless
Notes: called by MS-DOS 5+ IO.SYS and DR DOS 6.0+ IBMBIO.OCM startup code if
the signature "RPL" is present three bytes beyond the INT 2F handler;
this call overrides the value returned by INT 12
hooked by RPL code at the top of memory to protect itself from being
overwritten; DOS builds a memory block with owner = 0008h and name
"RPL" which must be freed by the RPL code when it is done.
Under DR DOS, it is sufficient to set the owner field of the MCB to
In addition to the test for "RPL", DR PalmDOS (since 1992/08/25),
DR DOS 6.0 "Business update March 1993", DR DOS "Panther" and
"StarTrek", and Novell DOS 7+ also check for a "RPLOADER" signature.
If this 2nd signature is found, IBMBIO.COM will store the INT 2Fh
vector for later use after the BIOS init, when at several points it
directly calls the RPLOADER via an emulated INT 2Fh with
AX=12FFh/BX=5/CX=0/DX=1 and a phase code 1, 2 or 3 on the stack.
This permits the RPLOADER to keep track of the initialization
process and clean or fix up anything it wishes. The "phase 1"
broadcast is issued after the BIOS init code and data have been
relocated (e.g. into the HMA), "phase 2" gets issued immediately
before the CONFIG.SYS processing begins and the DOS code and data
are relocated, and the closing "phase 3" happens to permit any
final tidy ups before the memory manager gets acknowledgement of
SeeAlso: INT 12"BIOS",INT 18"BOOT HOOK",AX=4A07h,INT 2F/AX=12FFh/BX=0005h