INT 1aH: Timer I/O (and MRCI POST Hook)

 INT 1aH services provide access to the system clock.  Also INT 1aH may be
 intercepted by a hardware-based MRCI compression system.
          AX    Service
          ▀▀▀▀▀ ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀
          b001H Query MRCI hardware support

          AH  BIOS Service              Supported by
          ▀▀▀ ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀ ▀▀▀▀▀▀▀▀▀▀▀▀▀▀
          00H read the clock (ticks)    [PC] [XT] [AT]
          01H set the clock (ticks)     [PC] [XT] [AT]

          02H read time from CMOS RTC             [AT]
          03H set the time on CMOS RTC            [AT]

          04H read date from CMOS RTC             [AT]
          05H set the date on CMOS RTC            [AT]

          06H set alarm on CMOS RTC               [AT]
          07H cancel alarm on CMOS RTC            [AT]

 The PC BIOS works with a "tick count" of the number of 55ms intervals
 which have occurred since the PC was turned on or reset.  The AT BIOS also
 provides access to the real-time clock values which are updated constantly
 without CPU action, and are stored in the AT's CMOS Memory.

 On AT-compatible machines, most short-interval timer/alarm operations are
 perfomed via INT 15H.

See Also: ROM-BIOS Functions
          MRCI API
          System Information Functions (DOS fns)
          BIOS Data Area (0040:006c)
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