Int 15 Fn C3  - System - Enable/disable Watchdog Timeout (ps50+)           [B]

   AH = C3h
   AL = function
       00h disable PS/2 watchdog timer
       01h enable PS/2 watchdog timer
       BX = timer counter (0001h-00FFh)
       02h disable Gearbox system
       03h enable Gearbox system

Return: CF set on error
   CF clear if successful

Note:  the watchdog timer generates an NMI

See Also: INT 21/AH=2Bh/CX=6269h"WDTSR"