Mac mini 2018 - Thermal management / Cooling solutions
 
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Mac mini 2018 - Thermal management / Cooling solutions  

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expensivefruit
(@expensivefruit)
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On the recommendation of @itsage, I have started this separate thread for us to discuss potential thermal solutions for the 2018 Mac mini. Here is a summary of where we are and what we know so far:

  • Manual control of fan not currently possible - @johnjkle has reported SpeedFan as not being able to detect a single fan.
  • Undervolting is not a solution on this CPU.
  • Exhaust fan to suck air out is unlikely to be viable - @danhc has pointed out that this could damage the internal fan by increasing its RPM.
  • Blowing fan to push air out has been developed for previous mac mini - there are no reports, however, of how effective this is or what damage it could cause to the internal fan. Other potential solutions, such as a laptop cooling pad, are also unknown quantities in both effectiveness and potential damage. 
  • Standing the mini on its side without lid has not been tested but the consensus so far is that this is unlikely to help anything.

 

Some have also reported that the fan is not very loud when the CPU heats up. This would imply that its not running to its full capacity or is simply not a very good fan. There may be therefore some potential solution down the line in terms of an Apple firmware update or a DIY fix through a third party application.

Others, such as @anethema, have pointed out the possibility of a 3D print solution: "considering the circle on the bottom is only a press fit, a neat part to model would be a 3D printed circle that press  fit in and has a mount for like a 120mm fan". This is similar in concept to the blowing fan developed for the previous mac mini.  

I will be purchasing my mac mini at Christmas but, until then, I will be brainstorming for solutions to this issue. In the meantime, I'm hoping we can all put our heads together and see what we can come up with! I will be updating this post as we go along.  

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

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mac_editor
(@mac_editor)
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@expensivefruit What about thermal repasting/liquid metal?

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expensivefruit
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@mac_editor I haven't seen anyone report anything yet but I've heard/read before that the thermal paste Apple use is pretty poor. I did see someone on macrumors post a photo where they applied more thermal paste after they added RAM, although this was before they even ran the god damn thing, so it's hard to say what their performance gain has been. I'll see if I can track down that post and ask the poster to run a test. What sort of gains do you think can be made using more and/or good paste? I have no experience in applying it so I'm not sure what the process is like - hopefully others can contribute on this.

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

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mac_editor
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@expensivefruit I have re-applied thermal paste only once, on my older 2014 15" MBP and the results were generally positive. Without changing any fan curves I noticed that the fans seldom ramped up in macOS post re-application on medium load. While the system still throttled at max. load (a given on something like an MBP), it occurred less often and less severely. I do not have numbers to back up my experience however. In my opinion a combination solution of good thermal paste and a better fan curve (if any app comes up that supports the same) would be a great starting point on the Mac mini.

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expensivefruit
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People on this forum seem to be suggesting that the mac mini already has a lot of thermal paste and any more could have the opposite effect.

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itsage
(@itsage)
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@expensivefruit The majority of Macs left the factory with more thermal paste than needed. I cleaned the CPU die and heatsink in my Mac mini when I had it apart. I then applied a thin coat of Thermal Grizzly Kryonaut using the included plastic spreader tool. My guess is the firmware is tuned for low noise rather than aggressive fan curve.

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mac_editor
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@expensivefruit Having more thermal paste is not the same as better performance. More can be bad as @itsage points out. Also the quality of thermal paste matters too. Apple has historically used poor compound. I did not suggest adding more thermal paste - rather replacing it with better compound (so one cleans off the previous paste completely and then re-applies the new one).

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expensivefruit
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@mac_editor & @itsage thank you both for clarifying. Is removing and reapplying an easy/straightforward process? Also, @itsage, do you think in your case it has helped at all? I expressed these thermal issue concerns on macrumors and someone who has already purchased their mac mini seems to be pretty insistent that the high temperatures are not something to worry about. When I pushed him on this he gave me this answer:

"Nobody is doing it consistently. I do video encoding twice a week. That's the only thing I do that stresses it. So not often.
Intel has spec limits on it, they have systems to slow the frequency down to reduce temperatures when they feel it's too hot. When encoding and mine is in the 90's it's still running above base frequency so they're clearly ok with it running at that temp otherwise they would throttle it sooner and more aggressively. I'm really not worried about it.

Maxing a CPU will push it's temp. Not just in a mini but even in your desktop PC's. Even my watercooled PC is still in the upper 80's when encoding. Imagine with just a fan on that! I encoded with previous computers with only a CPU fan and they would also hit the 90's. No issues. The system will shutdown to prevent damage though i've never actually seen it happen as it uses it's other systems to bring the temp down first."

Thoughts? 

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

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DanHC
(@danhc)
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@expensivefruit

(See 12:45)

In this video Linus did the exhaust fan trick and his laptop CPU got up to 5Ghz.
So Vacuum Fan solution must work. For the damaging the internal fan part, I am skeptical about, say if the fan run higher than its max speed (say 2000rpm) higher due to air being drag out of the cooling assembly, it won't exert much more friction on it to be honest. And even if it happens, I think Apple would still replace it.... all they could see from inspection is a "defective" fan..... haha

So if we vacuum air from mac mini's exhaust vent, I am sure it will work....... In extreme case, say we just connect a 2000W vacuum cleaner to it's exhaust and seal it off....... the wind will be so great that I doubt it will even hit 80C, but then will it be so strong it may suck the capacitors out of the board LOL

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mac_editor
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@expensivefruit Apple generally prefers low-sound-first fan curves and all their Mac products typically run hot. While it is true that nothing will happen to system even if it is running hot for long periods (example: my older 2014 MacBook Pro - did some encoding that lasted days, and frequently pushed it far and beyond with and without eGPU - never any issues or repairs needed - this is before thermal paste change - lasted 4 years until I just upgraded - it was fine), going the extra mile is certainly not a negative in any way (except perhaps one messing up something and destroying their board) in terms of life-lengthening or performance.

In summary, people aren't applying thermal paste to macs for longevity (they last long regardless), but to eek out any modest performance gains possible with better compound and if possible reduce throttling at high load.

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Master Threads:
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