I have a RK3588 (Radxa Rock 5C) system running Armbian Debian Trixie.  I have the heatsink and the fan installed as well.  I set the fan PWM to 255 as soon as temperature reaches 50 degrees via a systemd service.

 

When using all 8 cores, the system overheats (>110 degrees) and eventually shuts down.  For example, when compiling ffmpeg, it works fine with 'make -j6', but 'make -j8' results in a shutdown before compilation is complete.  Likewise I had thermal issues when using llama.cpp.

 

Shouldn't the OS throttle the CPU when temperature reaches high levels?  I think that is not happening at the moment. Online search referred me to cpufrequtils to set a conservative governor, but it looks like cpufrequtils does not exist for Trixie.

 

Any suggestions on how I should approach this?

I suggest to get a better heatsink and/or thermal paste/glue.

Next I would at the device tree if there are thermal points defined. Perhaps they are missing. You can use the dtc tool to decompile the device tree from /boot. Output values might be in hex instead of decimal, so just in case you wonder.

using cpupower to limit the max cpiu frequency to 1.61Ghz fixed the thermal issues.  Default was 1.8Ghz.  I'll might even reduce the max to 1.42, because USB hard disk mount drops when CPU usage is too high.

Note that I believe Armbian will reset the max CPU frequency on boot.

There is code in /usr/lib/armbian/armbian-hardware-optimization that uses the values defined in /etc/default/cpufrequtils to initialize the governor, min and max frequencies at boot time.  So even though cpufrequtils is no longer an installed set of tools, Armbian is still doing some of the same work based on its old configuration files.

So assuming this works as it used to, all you should need to do is set the max speed you want in /etc/default/cpufrequtils

Ah I didn't know about that. I just created a systemd service that runs cpupower at boot.