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=5306h,INT 2F/AX=1680h

See also: 151000

155305 - Advanced Power Management Specification - CPU IDLE