LOL I see, I was beginning to wonder why a certain vegetation could be involved in this...Pot = potentiometer = variable resister = what that fan controller you showed in your picture actually is...
I know you can't just resister-mod a pwm fan. Well, you can to a point because lowering the operating voltage will lower the revs regardless of what the pwm control lead tries to do...
Speedfan is on my list of things to try before anything gets modified.
The way I understand it is that it is interfaced via IPMI. The BMC does the interface with the FCB so if one is hotter then the others I would assume all the fans would come up to speed. If in fact the FCB does actually control PWM and not just monitor the RPM sensors.Very interesting. The only issue here is that there are four systems with four fans so there are some dependencies since it is not even a 1:1 ratio.
I think that would work as well then you would get the control from the FCB but also have it slower then what would normally be speced. We will have to wait and see if anything works in software first before hardware is needed.How about doing a uC reading the PWM coming from the PIC uC on the FCB and lowering the duty cycle that is seen by the fans?
Me too, one of my chassis has 5 hotswap fans and each fan sits on top of a circuit board that does automatic fan speed control. the board also allows manual override of fan speed by using a jumper.Looking for simpler solutions.
My guess has been that this is what we will come down to but I don't want to get in the way of anyone's creative process.After getting access to the actual photos of the Dell fans, it looks like the simplest way is just replace the fans with slower ones. (replace the fans by cutting the 4 wires and reconnect them to the new fans, and let the 2 extra wires and socket from Dell's original setup remains unaffected and continue to do whatever it does)