Re: [lm-sensors] pwmconfig/fancontrol error (version 3.3.1)

[Charles <c@catcons.co.uk>]

On 04/12/11 16:30, lm-sensors-request@lm-sensors.org wrote:
> Hi Charles,
> 
> Please keep the list CC'd.

Oops!  Sorry.

>> > Tested; no error messages and GKrellM shows sane processor core
>> > temperatures and fan speeds.
>> > 
>> > Sorry for the incomplete initial report:
>> > * I had applied the suggested workaround (thanks Jean and Guenter).
> Hmm. Please test the updated version of the script _without_ the
> workaround applied. That's the whole point of the update.

That's how I did test the update.  Should have made clear.

> Most likely because the CPU fan header is a 4-pin header, and the Intel
> CPU fan has 4 wires, while the case fan headers are 3-pin with a 3-wire
> fan.
> 
> On 4-pin headers, the PWM signal is separated from the power. So you
> can't control a 3-wire fan plugged in a 4-pin header (the PWM signal is
> on the unconnected pin [1].) This also explains the minimum speed of
> 4-wire PWM-controlled fans. This is per design. If the minimum speed
> doesn't please you, you have to either buy a different fan with a lower
> minimum, or lower the fan voltage using a serial resistor (Noctua
> amongst several other fan vendors includes such resistors in many of
> their product packages.)
> 
> [1] Some boards have jumpers that will let you turn a 4-pin fan header
> into a 3-pin one. You loose the benefits of 4-wire fans (such as linear
> fan speed control and reliable readings at low speed) but are no longer
> affected by the arbitrary fan minimum then.
> 

> Indeed, it is only recommended to connect similar fans to the same
> control output. There's a reason why board makers often connect the
> case fans together, but usually have a separate fan control for the
> CPU(s).

Thanks for explanations, Jean :)

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