INT 2F - Quarterdeck RPCI - GET QD HIMEM PRESENCE
AX = D201h
BX = 4849h ("HI")
CX = 4D45h ("ME")
DX = 4D51h ("MQ")
Return: BX = 4F4Bh ("OK")
ES:DI -> HIMEM entry point
Range: AH=C0h to AH=FFh, selected by scanning AH=D2h-FFh, then AH=C0h-D1h
SeeAlso: AX=D200h,AX=D201h/BX=5145h