INT 15 - Advanced Power Management Specification - CPU IDLE
        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
SeeAlso: AX=1000h,AX=5306h,INT 2F/AX=1680h

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