Prescott Series 600 power draw?

I ask this question out of curiosity rather than special need to know, but
maybe others are interested. I understand the Series 600 P4s (now in Dell
8400's) now bring "speed step" technology to the desktop, and WinXP SP2 will
be aware of this and step down the CPU when the load is light or maybe even
in response to rising temperature. I guess a P4 running at full speed can
consume something like a hundred watts. So what is the real-world power draw
of the CPU when there's no load? Will I really find the system using
significantly less power when it's not busy?

 

Enhanced SpeedStep Technology is included with the 660, 650, 640, and 630
processors (and the Extreme Edition).

The Thermal Control Circuit (TCC) will stop and start the processor to
reduce temperatures. These stops last no more than 3.0 microseconds and,
according to Intel, performance impact is immeasurable.

TCC2 is available only in the 660. TCC2 reduces power comsumption by
reducing the operating frequency and input voltage. Once cooled it will
return to normal.

I doubt any electricity will be saved, but the processor might be. ;-)

 

The spec sheet for the 6xx processors can be found here:
ftp://download.intel.com/design/Pentium4/datashts/30638201.pdf