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Just got a new Rpi gen #3, which has default /boot/config.txt has 

temp_limit=85

I then turn that down to 

temp_limit=70

after a reboot, it works. If you don't know how to stress the Pi processor, and how to read the temperature of that, feel free to clone my simple github code (shell script) and run that. 

 https://github.com/Fisherworks/raspberry_pi_stress

I thought it's dynamic lowering frequency which can limit the temperature of Rpi - but using the following command, it shows the frequency is still 1200000, which means it's running on full power.

cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq

Now the question is - How Raspbian control the temperature of BCM processor without reducing the freq?

Ning Yu Fisher
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1 Answers1

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Try this instead.

vcgencmd measure_clock arm

And you can check if it is being(has been), throttled, capped, or in under-voltage by this.

vcgencmd get_throttled

https://retropie.org.uk/forum/topic/2295/runcommand-warning-if-voltage-temperature-throttling

return code is like 0x50005.

bit pattern:

  • 0: under-voltage
  • 1: arm frequency capped
  • 2: currently throttled
  • 16: under-voltage has occurred
  • 17: arm frequency capped has occurred
  • 18: throttling has occurred

update: I know the command you used;

cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq

But it seems not used anymore and I found the new one being used;

sudo cat /sys/devices/system/cpu/cpufreq/policy0/cpuinfo_cur_freq

You can use it or vcgencmd.

Naohiro Tsuji
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  • I've checked the second command line again and found it's not working in kernel 4.4.45: `sudo cat /sys/devices/system/cpu/cpufreq/policy0/cpuinfo_cur_freq` but `vcgencmd` is ok even in 4.9.11. – Naohiro Tsuji Mar 06 '17 at 02:00
  • thanks for the answer @Naohiro. I got 0x50000, but still confused on the bit stuff, if the 0x50000 is a hex, then the bin should be 0101 0000 0000 0000 0000 so what you mean the bit 0 is the lowest one - the 0, and the bit 2 is also 0, which means it's currently not throttled? but the freq now is 600000, which is half of 1.2G - why it's not in throttling? – Ning Yu Fisher Apr 13 '17 at 11:03
  • You can use these command/scripts: `yes > /dev/null & # to increase the load, enter it 8 times or more.` `killall yes # release the load.` `while true; do vcgencmd measure_clock arm ; vcgencmd measure_temp; vcgencmd get_throttled; sleep 1; done` And you will see Raspi is taking rest when CPU load is lower. – Naohiro Tsuji May 10 '17 at 02:49