Raspberry Pi 4 & Heat If pushed the Pi 4 can heat up enough to require throttling its clock and voltage to cool down and avoid damage. There is a hard limit of 85°C and a soft limit of 80°C. The normal clock frequency is 1.5GHz and a documented minimum of 600MHz. Is the Pi part of the Train Thing application going to push the Pi 4 that hard? Don't know. A fan just in case.

After running a test program loop for 20-minutes (1200 seconds) to get a stable starting point, the following 10-minute run was recorded without a fan.

Raspberry Pi 4 no fan, 5-minute time/temperature graph

The CPU frequency was also monitored, but not shown. I think around 91 seconds into the test, where the temperature is around 65°C, the voltage is throttled to drop the temperature a couple of degrees. The recorded frequency did not change, and the test program is similar for the whole run.

Running the same exercise, 20-minute run followed by a 10-minute run, this time with a fan installed, shows a 17°C temperature drop for the run.

Raspberry Pi 4 w/ fan, 5-minute time/temperature graph

It looks like the temperature reaches equilibrium around 45°C with the fan running vs 63-64°C without the fan (and voltage throttling?).

An example of when the frequency dropped for a second is interesting. The yellow line in the graph below is the frequency, 1,500MHz and 600MHz, scaled to display with the temperature. During the frequency drop, the sample rate is an artifact of the loop time to generate heat. As revealed by the X-axis, this detailed graph was extracted from a 20-minute run.

Raspberry Pi time/temperature graph detail with freq drop

For completeness, two 20-minute graphs are included.

Raspberry Pi 4 no fan, 20-minute time/temperature graph

Raspberry Pi 4 w/ fan, 20-minute time/temperature graph

Graph Notes:

  • Each point on the graph represents a ±1°C or more change in the reported temperature, except during frequency throttling.
  • The graph represents 4-5 1°C changes in the reported temperature every second.
  • The 20-minute runs sometimes would have a single drop in clock Freq from 1,500MHz to 600MHz.
  • I think unmeasured the system throttles the voltage.