Int 2F Fn 1689  U - Ms Windows 3.0+ - Kernel Idle Call                     [W]

   AX = 1689h
   ???

Return: ???
Desc:  the Windows KERNEL idle loop calls this function, which VMM uses as an
     indication that the system is idle, which in turn generates INT 28
     and INT 2F/AX=1607h/BX=0018h callouts

See Also: AX=1680h,AX=1607h/BX=0018h,INT 15/AX=1000h,INT 28