
Actually, the iAPX86 family has a HALT instruction that causes the CPU to
cease processing instructions.  The CPU resumes processing either by being
reset or by receiving an external (hardware) interrupt.  This is different
from the power management facilities Victor mentions.  Of course, whether an
operating system's idle loop uses the HALT instruction is another matter
entirely.
-- 
Kenneth R. Ballou				VOICE:		 (617) 494-0990
Oberon Software, Inc.				FAX:		 (617) 494-0414
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