Yes and no

Subject: Yes and no
Name: ludicrous
Date: 1/7/2001 4:34:42 PM (GMT-7)
IP Address: 138.67.74.229
In Reply to: Can the cpu speed be changed dynamically? posted by Kurran
Message:

yes, some CPUs will permit on-the-fly, continuous speed changes, i.e. PowerNow! in the AMD K6-X+ processors.

In your case, you're dealing with the Suspend-on-halt (HLT) command, recognized by most modern microprocessors including Intel CPUs, in which unused CPU portions can be dynamically put into suspend mode.

Try some programming resource sites, perhaps Sanpile.org?