LinHT – SoM thermal management

Recently, Jacek SQ5BPF performed a very nice experiment. The question that we had was this: how does the SoM behave, thermal-wise, under heavy CPU loads? Is any form of cooling required?

Jacek plotted a temperature vs. time graph after logging its values for a while, using a simple bash script. It read the CPU’s thermal sensor at a fixed interval, while the machine was stressed with sysbench¹:

#!/bin/bash
#just get the temp from linht --sq5bpf
while : ; do
echo -n "$SECONDS  "
echo "scale=2;`cat /sys/devices/virtual/thermal/thermal_zone0/temp`/1000" | bc
sleep 1

The values were used as-is (the sensor is not calibrated). CPU stress was relieved after 10 minutes. Two test setups were examined: without thermal pads and with pads applied. Thermal conductivity reported by the manufacturer is 6 W/m⋅K.

The results are shown below.

The CPU clearly runs at much lower temperatures with the pads applied. The test has been conducted at ambient temperature of about 22°C. The CPU idles at 36.5°C with pads applied, which is over 5°C cooler than the baseline.

Thank you a lot for performing this experiment!

1. sysbench --time=600 --threads=2 cpu run ↩︎