Variable processor speeds?

In one of the posts here someone mentioned 200, 400, 800 and 1Ghz speeds for the processor. I see nothing about this in
the BBB manual PDF. How is this controlled?

From a HW perspective this is controlled by changing the clock speed of the processor inside the processor and lowering the voltage on the power rails using the power management IC. It is supported in the kernel.

You can find more information in the processor Technical Reference Manual found at

For the PMIC, you find this at


Thanks, Gerald. So what is the normal default speed that the processor runs at in the BBB?
Or does it vary depending on what? I only need high speed for short bursts of one second intervals.

Under Angstrom we generally we have the automatic mode on. It can vary between 300MHz 600MHz 800MHz and then 1GHz bases on the settings you pick. It has four modes, Conservative, ondemand, performance, and power save.

You can add a control for it by adding it to the top tool bar. To do that:

  1. hover the mouse over the top too bar
  2. Right click the mouse
  3. Click on Add Panel
  4. Then select CPU Frequency Scaling Monitor
  5. Select the Add button

Once installed hover the mouse over it an click the left button. You will then see what I described above. It also shows you the current processor frequency.


~# cpufreq-set
At least one parameter out of -f/--freq, -d/--min, -u/--max, and -g/--governor must be passed

~# cpufreq-info
cpufrequtils 008: cpufreq-info (C) Dominik Brodowski 2004-2009
Report errors and bugs to, please.
analyzing CPU 0:
   driver: generic_cpu0
   CPUs which run at the same hardware frequency: 0
   CPUs which need to have their frequency coordinated by software: 0
   maximum transition latency: 300 us.
   hardware limits: 300 MHz - 1000 MHz
   available frequency steps: 300 MHz, 600 MHz, 800 MHz, 1000 MHz
   available cpufreq governors: conservative, ondemand, userspace, powersave, performance
   current policy: frequency should be within 300 MHz and 1000 MHz.
                   The governor "performance" may decide which speed to use
                   within this range.
   current CPU frequency is 1000 MHz (asserted by call to hardware).
   cpufreq stats: 300 MHz:nan%, 600 MHz:nan%, 800 MHz:nan%, 1000 MHz:nan%