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This is a bit of a follow up to Why is my Pi running at 700MHz all the time? and Overclocking - CPU Frequency Measurement Accuracy: vcgencmd vs cpuinfo_cur_freq

I have a Raspberry Pi B3+ (at least that's as what I bought it).

I'm trying to figure out why my CPU seems never to run faster than 600Mhz:

vcgencmd measure_clock arm
frequency(45)=600000000

I enabled the performance governor:

echo performance > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor

Then I ran a stress test:

stress -c 4 -t 60

While that is running, I still get 600Mhz from vcgencmd measure_clock arm.

I did no special config or overclocking (yet):

grep freq /boot/config.txt 
#arm_freq=800

The default seems to be fine:

vcgencmd get_config arm_freq
arm_freq=1400

The Pi should be able to run at up to 1.4Ghz:

cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq
1400000

So what's going on here? What am I missing? Is my stress test wrong?

  • stress test looks OK - my pi3 goes to 1.2Ghz immediately using exactly that command line (well, almost exactly, I use stress-ng instead of stress) - you seem suspicious of what you bought - what is the output of grep Revision /proc/cpuinfo – Jaromanda X Oct 10 '18 at 22:11
  • It shows 4 cores identifying as ARMv7 Processor rev 4 (v7l), Hardware BCM2835 Revision a020d3 – Andreas Gohr Oct 11 '18 at 22:06
  • The command I asked you to run would've only shown the Revision :p I just wanted to see if you really had a 3B+ because you seemed unsure in your question. And yes, that Revision suggests you have a Raspberry PI 3B+ – Jaromanda X Oct 11 '18 at 22:12
  • Ah yeah, I somehow only read the /proc/cpuinfo part ;-) Anyway any idea what's going on? – Andreas Gohr Oct 11 '18 at 22:35
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It turns out the problem was the power supply. I was only rated for 1.5 amps and apparently that was not enough and the Pi throttled it self. A 3A supply fixed the problem.

Since I'm running this system headless and in a case, I neither saw the warnings during boot nor the power LED flashing.

If someone knows how to read the voltage warning in python, please let me know.

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