Confusion re: Intel P4 CPU documentation on Maximum Temperatures

[Zar1]

I am reading Intel's Thermal Specifications and Design Considerations and in Table 5-1 it lists the maximum case temperature for my P42.80C as 75C. But then in another document, Thermal Management for Boxed Pentium® 4 Processor-Based Systems, I read in Table 1 in the notes that 40C is the "Recommended maximum internal chassis temperature for boxed Pentium 4 processor-based systems."

Which is it? Are they saying they think you ought to keep the CPU below 40C, but that it can "handle" 75C before shutting down? Or is this 40C number only related to how fast the fan should run?

My CPU core normally runs at ~40C when under light loads and goes up to 60C when loaded more heavily (say, running a game like UT2003). Am I exceeding the maximum recommended temp or not?

 

[Mikewarrior2]

Internal Chassis temp = Case temp. They recommend a case temp of 40C or lower.


Mike

 

[WarCon]

You might also want to note that the 75C max temperature measurement is from a top dead center (on top of the heatspreader) thermal diode, which is not the temperatures that you read from the circuitry on your mobo (which is reading an internal diode and interpreting the data with its circuitry). Some motherboard manufacturers don't follow Intel's specifications for a lossless circuit for reading that diode to attain the voltage drop of that internal thermal diode, so their readings aren't accurate and should be used only for comparison sake. Abit says theirs is accurate (reads ~10C higher than most other manufacturers), but who really knows without them releasing their schematic.

One more thing to note is that P4's don't rely on the external circuit for catastrophic failure, they have a second internal thermal monitor circuit that will issue a complete stop command when it achieves an internal temperature of 135C.

 

[Zar1]

Mikewarrior,

Thank you very much for clearing that up. That makes much more sense, at any rate.


WarCon,

Thanks for the input. I did read about the Pentium's own internal shutdown mechanism that works independently of everything else. Of course, it also has clockrate throttling capability as well. Anyway, it was very helpful to hear your summary of that technology because it certainly helps clarify the issue.

BTW, I have an MSI 865PE Neo2 mobo. I am using both the "CoreCenter" monitor from MSI and MotherBoardMonitor (MBM) to monitor temps. The MBM website says that you need to add 4C to whatever it says for this MSI mobo. So if it reads 36C for the CPU, that's actually 40C, I think... Or maybe that means its really 36C but MSI's mobo "reports" 40C. Ugh. These differences can be confusing.