question about accuracy of onboard temperature sensor (BPi M2+)

[laibsch]

Hello,

 

I am curious to hear how accurate the measurement of temperature is from the onboard sensors, particularly in my case for the Banana Pi M2+.

 

While I do understand that the BPi M2+ suffered from poor choices for thermal management from the manufacturer both in hardware and software, I believe that thankfully Armbian has worked out the kinks on the software side, hasn't it?  I am running the latest noble image, here's what I noticed.  The temperature as shown by the sensors and armbianmonitor commands never really goes below 60° even on idle with ambient temperatures of around 25 to 30 degrees.  My SBC already came with a small heatsink attached to the CPU.  I found that value pretty high and inquired with an infrared thermometer but couldn't really find a spot on the board over 40°.  Which makes me wonder if the reading is accurate and properly calibrated?  My impression is that it is not.

 

Furthermore, I noticed the board behaves quite well under load.  For example, I stress-tested it with the yes command on all cores for about an hour or so and while the temperature went up to 95°, it appears the software was well-tweaked to only slightly throttle the CPU (verified with armbianmonitor -m) to not exceed this.  I am not 100% sure about the thermometer readings, but I believe they were around 60° at the time, certainly nowhere near what sensors was showing.  I have been testing the board for about a week now and I have to say that one time, the board did indeed shut down due to thermal overload.  Interestingly, this wasn't even when the CPU was heavily loaded but there was a lot of IO wait.  Temperature was high and it briefly shot up to 101° (ouch) which triggered an emergency shutdown to prevent thermal damage.  Looked good to me, mostly.

 

So, again, my question today is how trustworthy are the readings from the sensors, are they properly calibrated?

Edited 11 hours ago by laibsch