Can someone please tell me what the conditions should be to define the term "Idle Temperature" for a CPU, according to most specifications shown on websites for HSF's? Inotherwords, what are all the conditions that determine a valid reading of "Idle Temperature" for a CPU.

just leave the computer alone for 15mins, and take a look and the temp after those 15mins that would be your idle temp. E=MHZ

Press ctrl+alt+del to open task manager in win2k or win xp. The defintion of idling means your cpu ultiization stay from 0-5% range and you should not doing any work. If a program takes up more than 50% of cpu usuage even though you leave the computer alone, it is not idling... TMP-Man Asus P5P800-SE Pentium 4 506 2.66Ghz @ 4000Mhz @ 1.5125v 1024MB Dual Channel DDR400 40GB 5400RPM + 120GB 7200RPM HD 128MB Radoen 9500 mod 9700 @ 360/585

An idle temp means just that, like a car. You leave it running, but dont "use" it. P4 2.6gig, Gigabyte GA-8S648Fxm m/b, 1gb PC3200 RAM 80gig hdd, Ati radeon 9600 256mb graphics

With all due respect to the above replies, why is it no one mentioned the room temperature or case temperature as a factor in Idle Temperature?

room is not same as idle... Why simply because if your computer is idling, you still consume power but at a very low power... Unless you turn your machine off and you will have your room/case temperature same as your cpu temperature. But if your room/case temperature is 20C and your idling with a CPU that consumes 10watts in idling, by using heatsink thermal resistance of 0.30 C/W, you get 20C + 10 x 0.30 = 20 + 3 = 23C... But when your CPU is at full usage and consumes 100 watts, you get 20C + 100 x 0.30 = 50C at full load... You can say the case/room temperature has influence on temperature, but not same as idling, given if you do not enable "cool n quiet" on AMD CPU or "Enhance Halt State" on intel CPU, you will consume at least 50% of max watts... TMP-Man Asus P5P800-SE Pentium 4 506 2.66Ghz @ 4000Mhz @ 1.5125v 1024MB Dual Channel DDR400 40GB 5400RPM + 120GB 7200RPM HD 128MB Radoen 9500 mod 9700 @ 360/585

"With all due respect to the above replies, why is it no one mentioned the room temperature or case temperature as a factor in Idle Temperature?" Because this had nothing to do with his question, i.e. he asked specifically what idle temp is, not what factors contribute to idle temperature.