p870tm 2nd CPU fan port!

Discussion in 'Sager and Clevo' started by tanzmeister, Jan 9, 2018.

  1. ole!!!

    ole!!! Notebook Prophet

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    no, meant connecting wires to pin 2/3
     
  2. Meaker@Sager

    Meaker@Sager Company Representative

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    I believe there is no active control and it just sends a full speed signal all the time.
     
  3. ole!!!

    ole!!! Notebook Prophet

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    so whats the point of pin 2/3 then?
     
  4. Meaker@Sager

    Meaker@Sager Company Representative

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    Should the fan be used in a future model the sense pin sends back the current RPM to the EC which will have the sensor switched on, it would likely panic and shut down without an expected value. Also a fan curve will be programmed into the EC to control the speed compared to CPU temperatures. Since the production model does not use it then this is not currently there.
     
  5. ole!!!

    ole!!! Notebook Prophet

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    so how you know 870TM model doesn't have control to this 2nd fan port?

    if theres no control we maybe able to do a spliter from the main cpu pin
     
  6. Meaker@Sager

    Meaker@Sager Company Representative

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    From other tests and comments from Prema.
     
  7. ole!!!

    ole!!! Notebook Prophet

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    @poprostujakub @Meaker@Sager

    if primary cpu fan is controlled with just red/black, then we don't need the RPM signal for fan control by the mobo? any possible way to confirm this?

    these fans may or may not fit was thinking of using the 12v ones to do splitter from primary CPU fan
    12v, 0.18A https://www.ebay.com/itm/261875806386
    12v, 0.10A https://www.ebay.com/itm/322310113321
    5v, 0.4A https://www.ebay.com/itm/322133870001

    also no idea which one would be most powerful, going by numbers its 5v 0.4A but could be totally wrong here.
     
  8. poprostujakub

    poprostujakub Notebook Consultant

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    Mobo doesn't control fan by measuring its speed, there are fixed voltage levels (fan speeds) that are included in fan table in EC. RPM information is only for indication if fan is present. You can drive fan with external supply in whole speed range (and slightly beyond) and EC will not do anything as long as fan sends any signal via yellow wire.
    If you buy 12V fan, you'll be able to simple connect it parallel with main fan. But I'm worry about maximum current capability of driver IC. Theoretically, driver should be able to drive fans with current consumption up to 0,7A, but any device that contains electric motors, including fans, draws more current at startup and can trigger short circuit protection in IC. It's not dangerous, because driver IC will recover itself from short circuit protection mode to normal mode, but EC probably will start "fan-missing" shutdown procedure.
     
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  9. ole!!!

    ole!!! Notebook Prophet

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    if we go by hard number, primary cpu fan is 0.5A and we get 2nd 12v fan say 0.1A and run it parallel to primary fan. would 2nd 12v fan speed be controlled by EC as well or would it constantly be at max, or would that be dependent on the 2nd fan specification what its capable of?
     
  10. poprostujakub

    poprostujakub Notebook Consultant

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    As I say earlier, speed of main fan is controlled by its supply voltage - 12V for max speed and probably 6V for minimum speed. So second fan, connected identical as main fan, will change its speed identical as main fan. Except, if second fan have higher start voltage (typically 12V fans have start voltage around 7-8V, but I don't know if this is also true for small fans), because on lowest RPM levels this fan can sometimes squeaks. I faced this situation once, when I tried to lower minimum GPU fan speed in my P375SM - with default voltage of 2,5V, I set 2,2V and fan started squeaks like coils, but louder. On 2,35V this fan worked good without any collateral effects.
     
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