Is Your P4 Working At Half Speed?

ArneD writes: "While browsing xbitlabs.com discussion-board I found this message about the P4. The message suggests that the P4, when stressed and getting hot, starts to halt 50% of the time. When checking mail your precious P4 works at 1.5Ghz but when used for something meaningful (recompiling your kernel?!? ;-) the processor may in fact be a mere 750Mhz since it starts to issue PROCHOT signals that tells the processor to switch itself on/off 50% of the time until it's temperature is within Intels spec-range again." (Read more.)

"More information can be found in Intels Pentium 4 Thermal Design Guidelines (check out page 23)."

Several readers have submitted news of this clock-throttling, one aspect of the P4's built-in temperature sensor system Intel calls "Thermal Monitor." One thing to point out is that the same design guidelines document goes on to say that "the clock modulation feature of Thermal Monitor is disabled by default ... OEMs are expected to enable the thermal control circuit while using various controls and outputs to monitor the processor thermal status." Other things being equal (even if they never are) is there some reason to prefer a chip for not having this capability? If someone forced me to accept a free and loaded P4 system, I'd rather it be cool down at 750MHz temporarily than toast at 1.5GHz.