INT 15 - READ JOYSTICK SWITCH SETTINGS (AT,XT2,XT286,PS)
        AH = 84h
        DX = 0
Return: AL = switch settings (bits 7-4)

INT 15 - READ JOYSTICK INPUTS (AT,XT2,XT286,PS)
        AH = 84h
        DX = 1
Return: AX = A(x) value
        BX = A(y) value
        CX = B(x) value
        DX = B(y) value