Format drive starting at given track (XT,port)
        (harddisk only)

        Entry:
          AH = 07h
          AL = interleave value (XT only)
          ES:BX = 512-byte format buffer, see AH=6 above
          CH = cylinder number (bits 8,9 in high bits of CL)
          CL = sector number
          DH = head
          DL = drive
        Return:
          AH = status code (see AH=1 above)

        Note:   AWARD AT BIOS extended to handle more than 1024 cylinders by
                placing bits 10 and 11 of the cylinder number into bits
                6 and 7 of DH apparently, the AMI BIOS also follows this
                convention