INT 4Ah (74)             User Alarm                   XT-286, AT, Convertible

    Called by the Real-Time Clock (RTC) interrupt handler when the real-
    time clock alarm conditions are meet.

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    By default, the interrupt handler for this interrupt IRETs to the
    caller. The user can supply a handler that will gain control whenever
    the current time is equal to the alarm time. Make sure this interrupt
    handler is installed before using INT 1Ah, Service 06h, to set the
    real-time clock alarm.

       Notes:         This service is available only for the AT, XT-286,
                      and PC Convertible.

                      The Real-Time Clock (RTC) interrupt handler is INT
                      70h for the AT and XT-286. The PC Convertible uses
                      INT 08h (System Timer).