Source : Free On-Line Dictionary of Computing

Auto Idle
     
        A facility provided by some {Intel} {clock doubled}
        {microprocessor}s where the internal clock can be slowed to
        the external {clock rate} while the processor is waiting for
        data from memory, returning to full speed as soon as the data
        arrives.
     
        See also {System Management Mode}.
     
        (1994-11-09)