I have a 2012 mac mini that mac a weird breathing noise when under heavy CPU loads.
I removed the plastic bottom while running the CPU under load and what happens is the fan stops and and then starts up again repeatedly, causing this weird breathing. I've have a 2011 Mac Mini and on occasion hear the the fan ramp up and and eventually back down over time but I've never heard this kind repeated stopping and starting of the fan. I figured the fan just needed to be replaced which I did and then ran my tests again only to hear the breathing return. So it's not just a faulty fan and I've concerned that the processor will at some point overheat. It boggles my mind that the fan repeatedly stopping and restarting is normal behavior and i don't see how It can be the best way to cool the mac mini when under CPU load. Any ideas??

maybe a bum temp sensor somewhere?

Install Intel Power Gadget and look at the CPU use and temperature when the fan is having it's problems.

Then you could consider installing Macs Fan Control and set the CPU Temp or CPU PECI to ramp up the fan from 50-90C and see if the fan is actually paying attention to that control.



Edited 1 time(s). Last edit at 09/15/2021 11:47AM by Lew Zealand.

Remove dust bunnies?

Many thanks for the tip. Fan controller software seems to be working, so far.
Is there any fan control software that let's you define a minimum fan speed of 2000 RPM
and a max fan speed of 3,500 RPM??

I'm not aware of any that gives that fine control of speed but you really don't want your CPU to be over 95C and only spinning the fans at 3500 RPM when they can do 5000 and actually keep the CPU cooler. Running at 95C too much will lead to an early death though with a 9 year old computer you've gotten good life from it already.

In your case maybe try setting the ramp from 70C-100C so that it only goes over 3500RPM at 80-85C which seems a reasonable compromise.

Try smcFanControl

I'm curious whether your fan actually stops completely or just drops to a low speed.

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AllGold
Try smcFanControl

I'm curious whether your fan actually stops completely or just drops to a low speed.

Before I used the fan control software I opened the bottom of the mac mini while I stress tested and the fan would stop briefly before it started back up again. Based on what I've since heard with the fan going full blast (while testing the fan controller software) at 5500 RPM, it never got anywhere close to that speed. I would guess the fastest it ran under load would be roughly 3000. Which can't be good for the processor.



Edited 1 time(s). Last edit at 09/15/2021 09:43PM by prof.

The fans in both my mini and MacBook Pro always ran slower and with a higher CPU temperature than I would have expected. I know the CPU is rated for a pretty high temperature but, like you, I always thought it would be better to keep it cooler.

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AllGold
The fans in both my mini and MacBook Pro always ran slower and with a higher CPU temperature than I would have expected. I know the CPU is rated for a pretty high temperature but, like you, I always thought it would be better to keep it cooler.

That's Steve Jobs and Apple right there. Run quiet at all costs.

I do not agree with that as heat is the enemy of electronics, so I have Macs Fan Control (others use smcFanControl) on everything, usually setting fans to ramp up from min to max from 50-90C.