Int 15 Fn 5305  - Advanced Power Management Specification - CPU Idle       [p]

   AX = 5305h

Return: after system leaves idle state
   CF clear

Notes: call when the system is idle and should be suspended until the next
     system event or interrupt
   should not be called from within a hardware interrupt handler to avoid
     reentrance problems
   if an interrupt causes the system to resume normal processing, the
     interrupt may or may not have been handled when the BIOS returns
     from this call; thus, the caller should allow interrupts on return
   interrupt handlers may not retain control if the BIOS allows
     interrupts while in idle mode even if they are able to determine
     that they were called from idle mode
   the caller should issue this call continuously in a loop until it needs
     to perform some processing of its own

See Also: AX=1000h,AX=5306h,INT 2F/AX=1680h