INT 31 P - DPMI 0.9+ - GET FREE MEMORY INFORMATION
        AX = 0500h
        ES:DI / ES:EDI -> buffer for memory information (see below)
Return: CF clear
Notes:  16-bit programs use ES:DI, 32-bit programs use ES:EDI
        this function must be considered advisory because other applications
          may affect the results at any time after the call
        fields not supported by the DPMI implementation are filled with
          FFFFFFFFh
        DPMI 1.0+ supports this function solely for backward compatibility; use
          AX=050Bh instead
SeeAlso: AX=0604h

Format of memory information:
Offset  Size    Description
 00h    DWORD   largest available block in bytes
 04h    DWORD   maximum unlocked page allocation
 08h    DWORD   maximum locked page allocation
 0Ch    DWORD   total linear address space in pages
 10h    DWORD   total unlocked pages
 14h    DWORD   free pages
 18h    DWORD   total physical pages
 1Ch    DWORD   free linear address space in pages
 20h    DWORD   size of paging file/partition in pages
 24h 12 BYTEs   reserved