[bobsterlobster]

MSI shipped a genuinely good motherboard and forgot to wire one chip, so PWM doesn't work. Instead of tossing the board or living with the noise, I decided to make lemonade.

An Arduino Nano generates the 25kHz PWM signal, and a companion Windows application reads CPU temp and sends the duty cycle over serial. The Arduino firmware is open source (MIT).

[gzread]

What if Windows crashes? It's better to attach a thermal sensor to the heatsink, I think.

[johndough]

Just send a heartbeat every few milliseconds and set fan speed to 100% if it died. Bonus: You get an audible indicator that the system crashed.

[crote]

Well, what if?

We don't live in the AMD Athlon era[0] anymore. Modern CPUs are designed to boost until they hit a thermal limit, improper cooling is just going to result in a lower clock speed.

[0]: https://youtu.be/UoXRHexGIok?t=55

[bobsterlobster]

What a blast from the past. I still remember seeing it for the first time on my Socket A Athlon 1900+ pc.

[joe_mamba]

Damn, that video took me waaay back.

[bobsterlobster]

If windows crashes, then the audio generation crashes, so the fan will start to operate without PWM. Should default to 100%. At least that's how the PWM fans I have behave when the PWM signal suddenly disappears.

[haktan]

Could you use an audio out port for creating the signal and ditch the Arduino?

[magicalhippo]

That might work for the PWM signal, however you'd still need some electronics as the fan has internal pull-up to 5V and expects it to be pulled low by the PWM signal.

But a small circuit with a Schmitt-trigger inverter IC and some resistors and capacitors might do the trick, for example.

[bobsterlobster]

Interesting idea, I'll look into it.