Int 15h, 84h            Joystick Support                                 many

    Reads the current joystick switch settings or reports the current
    joystick resistive inputs.

        Entry   AH = 84h
                DX = Subservice
                     | 00h - Read current switch settings
                     | 01h - Read resistive inputs

        Return  CF Set if error, else cleared
                AL = Bits 7 to 4 contain switch settings
                or
                AX = A(x) value
                BX = A(y) value
                CX = B(x) value
                DX = B(y) value

    This service is available only for the AT, XT dated after 11/08/82,
    and XT-286.