Int 10 Fn BF0F  - Video - Compaq Extensions - Set High Adress Map Registe  [b]

   AX = BF0Fh
   BX = high address map location in megabytes, or
       0000h to disable high address map, or
       FFFFh to let ROM configure high address map

Return: CF clear
   AX = previous value of high address map register

Notes: supported by at least the QVision board and the SystemPro XL and LTE
     Lite ROM BIOSes

See Also: AX=BF10h