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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 workstations
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 0000h.. 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 completion.
See Also: INT 12"BIOS" - INT 18"BOOT HOOK" - AX=4A07h - INT 2F/AX=12FFh/BX=0005h Category: DOS Kernel - Int 2Fh - D
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