Dangerous CPU / GPU temperatures ?

[Parowdy]

First thing I'd do: Crack open the case ( not a lovely job on a slim iMac), repaste the CPU and GPU, clean out fans and check fan is working properly and is not obstructed.

You’d really mess with the hardware before checking potential software issues and fixes? Brave, and maybe overkill.

 

[Happy_John]

You’d really mess with the hardware before checking potential software issues and fixes? Brave, and maybe overkill.

Experience. Knowing these era of iMacs, the age of machine and the details given, it’s likely.

One wy or another, the internals need to be cleaned and the chips repasted.

 

[Parowdy]

I come from a PC world and in there, oftentimes there is a BIOS setting to run the system in Performance/Standard/Silent modes. Performance turns on the fan sooner/faster spin to keep temp low, Silent mode keeps the fan speed to its minimum to give noise priority over temp, and Standard is the middle compromise.

Don't the Macs have similar settings?

No. Apple decides how the fans and system behave, unless you use an app to overwrite what’s possible.
Newer Macs appear to have good heat management systems out of the box, but Intel Macs suffered from Apples obsession with thin and silent machines.

 

[pshufd]

I was waiting for someone to say that - there's always one in the crowd to defend the 100c mark. Don't forget if the cpu is near 100c, then its really toasty on the other internals which are a lot more sensitive to the heat, such as the VRMs, SSDs, etc.

Its generally acceptable to deal with spikes of 90c and above, but not constantly at +90C

What is a normal temperature for a CPU?


Safe CPU Temperature Range: What Temp Should My CPU Be?

My iMac Pro is currently running around 42 degrees. It gets up tot he high-50s.

My 2015 iMac 27 would get up to 70 degrees.

My 2015 MacBook Pro would get up to 70 degrees but I bought an external fan that would keep it at 60.

Yes, the design threshold is 100 degrees but I don't want a MacBook on my lap at that temperature, fans going crazy and the sound, or potential damage to other components due to high thermals.

My Windows PC is running at 33 degrees but it was designed to run cool and quiet when I built it.

My Studio is running at 35 degrees and is silent.

I don't like high thermals also because of higher AC costs.

 

[pshufd]

@maflynn @Romain_H,

I appreciate the help you both seek to provide and I thank you for it.
I think there is some truth in both speeches and that is what will encourage me to do what is necessary, measuredly, to make this computer that I love last, even if perhaps it means limiting it to less demanding tasks.

Thank you and all the contributors to this post 👍

You have a lot of components to look at to diagnose this.

Are there any crash dumps available to look at? Those often point specifically at the issue though it could be hardware or software. Have you consider trying a different version of macOS, maybe on an external SSD?

What peripherals do you have attached to the iMac as I've seen external devices as the cause to many crashes? It's often one of the first questions I ask when looking at a crash dump.

My daily driver is an iMac Pro and I love using it; many wish that Apple would make an Apple Silicon version of the iMac 27 for the screen, speakers, microphones. So I'll just keep using mine until Apple ends support for it. I can appreciate why you still want to use it.

 

[wave84]

My 2020 iMac temps have dropped by 10 degrees at least, after I serviced it this summer for dust cleaning and thermal repasting.

 

[MortyMars]

My iMac Pro is currently running around 42 degrees. It gets up tot he high-50s.

My 2015 iMac 27 would get up to 70 degrees.

My 2015 MacBook Pro would get up to 70 degrees but I bought an external fan that would keep it at 60.

Yes, the design threshold is 100 degrees but I don't want a MacBook on my lap at that temperature, fans going crazy and the sound, or potential damage to other components due to high thermals.

My Windows PC is running at 33 degrees but it was designed to run cool and quiet when I built it.

My Studio is running at 35 degrees and is silent.

I don't like high thermals also because of higher AC costs.

How do you proceed with your temperature measurements?

A third-party software?

On the command line?

 

[MortyMars]

Hi @pshufd

Are there any crash dumps available to look at?

Yes, I have attached restart reports in my posts n°3 and n°14

Have you consider trying a different version of macOS, maybe on an external SSD?

I admit that no, not for now.
But it will be part of the tests I will do as a last resort

What peripherals do you have attached to the iMac as I've seen external devices as the cause to many crashes?

Of memory, none, not even an external HDD or SDD.
Nothing but an Apple bluetooth keyboard and a Logitech bluetooth mouse as well, which have never caused a problem

 

[MortyMars]

Hi everyone,

I'm back in front of my capricious iMac and I did some of the manipulations you told me:
- Reset SMC + PRAM
- SSD test with DriveDX: No problem found
- 'Apple Diagnostics' at startup: No problem found
- I installed and configured Mac Fans Control so that the fan triggering at a temperature rise is more responsive
- And I did some maintenance operations with CleanMyMac and OnyX

No new untimely restart observed for the moment.
I cross my fingers.
I'll keep you informer