INT 08h (8)              System Timer

This interrupt is a hardware interrupt (IRQ 0) activated by the system
timer 18.2 times per second (every 55 ms). The default handler does
the following:

    Keeps a count of the number of timer ticks at memory location
0:46Ch (System Timer Counter  long integer). After 24 hours of
operation, a flag is set at memory location 0:470h to signal
this condition and the System Timer Counter (0:46Ch) is reset to

    Decrements the Diskette Drive Motor Off Counter at memory
location 0:440h if it is not 0. When this location reaches 0,
the diskette drive motor is turned off and the Diskette Drive
Motor Status byte at memory location 0:43Fh is updated to
reflect that the motor has been turned off.

    Generates INT 1Ch.

    For the PC Convertible, generates INT 4Ah if an alarm interrupt

See also: INT 1Ah, 06h
See also: INT 1Ch
See also: 0:46Ch
See also: 0:470h
See also: 0:440h
See also: 0:43Fh

INT 08h (8) System Timer