CPU temperature sensor output

Hi all,

I'm reposting this under General Motherboard because it seems more appropriate than Chipsets and BIOS.

Basically, my question is: Do motherboards have a pin which outputs the CPU temperature as an analog voltage (or as PWM, or anything else). I'd like to make a front-panel temp display purely in hardware, without using Hmonitor or other software.

If there's no dedicated pin on any motherboards for this, what's the easiest way you can think of to get a voltage signal of the CPUs internal thermosensor?

Thanks.
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  1. A great question. I've only found this very ollllddddd software-based version: http://forums.pcper.com/showthread.php?threadid=205049

    I'm assuming though that it's possible to split the CPU fan pin (where you connect the CPU fan) and grab the data from there? What do you think?
  2. Hmmm. I never thought of that question.

    r_manic said:

    I'm assuming though that it's possible to split the CPU fan pin (where you connect the CPU fan) and grab the data from there? What do you think?


    Unfortunately, it looks like the answer is "No". See page 85 of:
    http://download.intel.com/design/processor/datashts/318732.pdf

    According to the PECI (Platform Environmental Control Interface), the control signal for the fan does not represent a linear response to the output of the temperature sensors.
  3. r_manic said:

    I'm assuming though that it's possible to split the CPU fan pin (where you connect the CPU fan) and grab the data from there? What do you think?


    You know, that's a good idea. The only headache would be calibrating it; i.e. figuring out precisely what fan control signal corresponds to what temperature. It's doable, though. Thanks for that.
  4. jsc said:
    Hmmm. I never thought of that question.


    Unfortunately, it looks like the answer is "No". See page 85 of:
    http://download.intel.com/design/processor/datashts/318732.pdf

    According to the PECI (Platform Environmental Control Interface), the control signal for the fan does not represent a linear response to the output of the temperature sensors.


    Thanks for that great link. A linear response would be really nice, but it's not totally necessary, as maybe I could build some hardware (with a microcontroller, maybe) to turn a PWM signal or whatever else into a temperature reading. At this point, though, it's looking like a software solution is the way to go.

    I'm an electrical engineer but I'm just getting into PC hacking, so your link was really useful. I'm going to hunt down the PECI specs now. Seems like a lot of fun to be had.
  5. It is possible. CPU temp is monitored by the super I/O chip via one pin. Your dilemma however, will be that unless you perfectly duplicate the signal, tapping into it will bring it down low. The super I/O will not have an accurate readout and can cause premature shutdowns of the system due to false readings.
  6. infyrno917 said:
    It is possible. CPU temp is monitored by the super I/O chip via one pin. Your dilemma however, will be that unless you perfectly duplicate the signal, tapping into it will bring it down low. The super I/O will not have an accurate readout and can cause premature shutdowns of the system due to false readings.


    No problem! Buffer amplifier to the rescue! This would be a workable way to do it in hardware, actually, except that I can't find a datasheet for the Asus F8000 Super I/O chip on my mobo. It seems that none of the Super I/O chipmakers release datasheets to the public, actually. How did you get your information?
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