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JM3 4 pin header what is it for? 3090 ftw3

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Redtwofish
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2021/01/23 18:16:53 (permalink)
There is a four pin labeled JM3 under the rgb 3 pin header what is it's purpose?
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    ty_ger07
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    Re: JM3 4 pin header what is it for? 3090 ftw3 2021/01/23 21:23:47 (permalink)
    JM3 (blue), JM4 (tan), and JM5 (black) are each for the fans.  One fan for each connector.  They are PWM fan connectors.  One pin is power, one pin is ground, one pin is tachometer feedback, and one pin is PWM control signal.
     
    There is also another JM3 header by the RGB header.  It is also for a fan.  It's there so that you can add a case fan to run at the same duty % as the JM3 fan on the card.
     

    post edited by ty_ger07 - 2021/01/23 21:30:34
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    Dabadger84
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    Re: JM3 4 pin header what is it for? 3090 ftw3 2021/01/23 22:29:54 (permalink)
    Wouldn't recommend running a fan off the GPU's fan header, as that could further impact (negatively) the power limit on the card being utilized by the actual card, but it's for another fan, the 3 are for the on board fans on a FTW3 card as is indicated above.

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    ty_ger07
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    Re: JM3 4 pin header what is it for? 3090 ftw3 2021/01/23 22:39:12 (permalink)
    Dabadger84
    Wouldn't recommend running a fan off the GPU's fan header, as that could further impact (negatively) the power limit on the card being utilized by the actual card, but it's for another fan, the 3 are for the on board fans on a FTW3 card as is indicated above.


    You can run a nearly infinite number of fans off of the GPU's fan header without affecting the power limit of the card in any way.  The trick is to only connect to the PWM pin on the card, as that is the only pin necessary to control a PWM fan.  The PWM wire is a high impedance signal and draws an almost immeasurable amount of power.
     
    But, yeah, if you use the most generic and simplest approaches, you are correct.
     
    There are a lot of options for "splitter cables" which provide their power from a molex connector.  It is very easy to do it yourself, but if you don't have soldering skills, buy a powered splitter cable or "hub" (essentially a splitter cable on a PCB) to obtain this outcome.  As long as the fans get their power and ground from the PSU instead of the card, the power of the card is not affected in any way.
     
    Like this, which I have linked to in these discussions in the past:
    https://www.amazon.com/Cable-Matters-2-Pack-3-Fan-Splitter/dp/B01DV1Z0WC
     
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    And then there is my hack. Very homemade. Fabricated thermistor cable with parachute cord covering, epoxied into a fitting, to connect to a purchased fan controller board, connected by single pin to a cheap Arduino-compatible board to adjust ramping rate, create "zero-dB" radiator fan feature, and adjust pump baseline RPM and ramp independent of fan ramp.

     
    Looks VERY messy from the backside, but clean from the viewable side.
    close

    post edited by ty_ger07 - 2021/01/24 07:33:12
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    Redtwofish
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    Re: JM3 4 pin header what is it for? 3090 ftw3 2021/01/24 02:14:54 (permalink)
    Thanks👍
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    Kevin115
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    Re: JM3 4 pin header what is it for? 3090 ftw3 2021/01/24 07:44:10 (permalink)
    ty_ger07
    JM3 (blue), JM4 (tan), and JM5 (black) are each for the fans.  One fan for each connector.  They are PWM fan connectors.  One pin is power, one pin is ground, one pin is tachometer feedback, and one pin is PWM control signal.
     
    There is also another JM3 header by the RGB header.  It is also for a fan.  It's there so that you can add a case fan to run at the same duty % as the JM3 fan on the card.
     



    This is useful. Thank you.
    #6
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