I had a Squirrel moment, after completing the testing in The Road to Raspberry Pi4B/ PoE Hat RoadTest Review (comparison Pi3B+) . A squirrel moment going off and doing something, that takes you away from your current focus.  I was focusing on developing a load test for PoE and then thought I wonder how the Pi performs with just heat sinks and no fan.


The PoE Hat contains a fan to cool it's switching power supply that converts the incoming 48VDC to the supply voltage needed by the Pi. With the PoE Hat sandwiched together with the Pi, the fan is located over the Pi CPU. The Pi gets the benefit of the PoE Hat fan.


Squirrel moment, I wonder what the temperature differences are between a Pi with a fan and a Pi with just heat sinks. Yeah, I know, why do this when I can go find this information with a quick Google search. But heck, it is not truly a squirrel moments if you don't go for the chase when they come.


I pulled a new Pi3B+ from a box and installed heat sinks on the SoC, Fast Ethernet chip and the one chip on opposite side (couldn't find an identifier in my short search) of the printed circuit board. I then ran the stress and cpuburn tests and took screen shots of the results.

After a little over ten minutes the CPU hovered around 60 Degrees Celsius. Cool.


Running the cpuburn test some interesting observations. Long before ten minutes the CPU temperature had reached 80 Degrees Celsius but then the CPU frequency (i.e. number after the temperature started to decrease). The CPU temperature continued to hover around eighties while the CPU frequency never increased. I've read about this throttling effect but never actually went and explored it.


I did go and do a Google search to uncover some details to include in this Blog post. I discovered this test is really basic in comparison to some of the extensive tests returned from my search. I particularly liked one test returned in my search. It was infra-red camera shots with a Pi under stress.


Social isolation because of public health restrictions gave me the time to pursue it. I'm also retired which is a bonus. I rather enjoyed pursuing this squirrel moment.