0040h:0012h           Reserved (POST Status on PC Convertible)

    Length: 1 byte

    This byte is reserved by all machines but the PC Convertible and
    the PCjr. The PC Convertible uses it to hold the status of the
    POST (Power-on Self Test) operation. The PCjr uses it to count the
    number of keyboard transmission errors encountered in the infrared
    link.