Is a fan required for proper thermal management on Apalis iMX8QM?

Is a fan for active cooling required on the Apalis iMX8QM? If so, which kind of fan is required?

First off, it is safe to operate the Apalis iMX8QM without fan. The SoC will throttle GPU/CPU at 85°C temperature which will affect performance, but it won’t do any damage to the hardware. In fact, internal tests even showed that throttling works nicely even without heatsink at 125°C the system will do a thermal shutdown. But operating without heatsink is definitely not recommended!

At 85°C and higher the GPU is throttles rather extrem to a 1/64 of its regular performance. Which is often a problem in real world applications. Hence you typically want to cool the system to operate below 85°C.

[ 1649.875796] System is too hot. GPU3D will work at 1/64 clock.
[ 1650.255775] Hot alarm is canceled. GPU3D clock will return to 64/64

Whether active cooling is needed ultimately depends on your application. Running glmark2 (which loads the GPU) and load two A53 CPUs fully allowed to run the system over longer period of time without throttling (>20min). However, when loading all cores, the system started to throttle after about 2 minutes.

During development it is likely not yet needed to run the CPU and GPU over longer periods of time at full load, so operating without fan is probably for a lot of development activities just fine.

In a final system, more factors need to be considered, e.g. beside typical CPU/GPU load also things like varying ambient temperature or casing. E.g. a fan is not very helpful if the case is closed anyway…

You can read the temperature of the system using sysfs. There are 5 thermal zones:

/sys/class/thermal/thermal_zone0/temp: A53
/sys/class/thermal/thermal_zone1/temp: A72
/sys/class/thermal/thermal_zone2/temp: GPU0
/sys/class/thermal/thermal_zone3/temp: GPU1
/sys/class/thermal/thermal_zone4/temp: DRC

If you want to be on the safe side, plan with a fan!

Fan: The screw holes in the heat sink fit a regular 40x40mm fan. Be careful to not use too long screws since the screw holes go through the heatsink and screws could touch (destroy) the modules PCB! The Mini-Kaze SY124010L and the Noctua NF-A4x10 FLX are two fans we currently use at Toradex. Both of those Fans fit with M2.5x14 screws.

Thanks for pointing out FAN models. My board is getting quite hot even while compiling. I’ve got Mini-Kaze fan from Amazon but it just came without screws. Would you mind telling what kind of screws supposed to be used? Really do not like to go to a hardware store with the board.

You can use that screws - https://www.amazon.com/XunLiu-Button-Socket-Screws-M2-5X14/dp/B0756SDFD2

Or any other M2.5x14 screws