Compatibility: EMS 4.0+
Expects: AH    5aH
AL    subfn: 00H=Allocate standard 16K pages
BX = desired number of standard pages
01H=Allocate raw pages
BX = desired number of raw pages
Returns: AH    EMM status (0=successful)
DX    EMM Handle
Info: This is designed for use by operating systems only and may be
disabled at any time.

This allocates EMS memory, as with INT 67H 4300H, but can
allocate "raw" pages (other than 16K) on the rare EMS board that
supports that oddness.

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INT 67H 5axxH: Allocate Standard or Raw Pages