Int 1Ah, 08h            Set Clock-Activated Power-On Mode         Convertible

    Sets the time at which the computer will automatically power on.

        Entry   AH = 08h
                CH = Hours (BCD)
                CL = Minutes (BCD)
                DH = Seconds (BCD)

        Return  CF   Set if clock not operating or alarm already set;
                     else cleared

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    This service is available only for the PC Convertible. Previous
    machines will report unpredictable results (including the state of
    the Carry Flag). ATs, XT-286s, and the PS/2 family will set the
    Carry Flag, thus reporting an error state.

    All dates are in Binary Coded Decimal (BCD). For example, June 1,
    1985 will be set as CX = 1985; DX = 0601.

    The real-time clock is the clock that runs even when the computer
    is turned off. A CMOS battery is used so that, even while the
    computer is off, the date, time, and alarm time are maintained.

    After this service is executed, the machine will automatically
    power on as soon as the hour, minute, and second specified match
    the time on the real-time clock date. If the system is already on,
    then Int 4Ah (User Alarm) will be executed.

    If the system is on, the alarm interrupt (Int 4Ah) will continue
    to occur every 24 hours at the specified time until it is reset
    via Service 07h (Reset Real-Time Clock Alarm). Only one alarm time
    can be active at a time.