라즈베리 저전력 발악해보기?

테스트 해보니.. maxcpus는 작동하지 않는듯

# replace N with the number of cores you want to keep using maxcpus=N

[링크 : http://raspberrypi.stackexchange.com/questions/32562/how-to-make-the-raspberry-pi-consume-less-power]

arm_freq Frequency of the ARM CPU in MHz. The default value is 700. core_freq Frequency of the GPU processor core in MHz. It has an impact on CPU performance, since it drives the L2 cache. The default value is 250. sdram_freq Frequency of the SDRAM in MHz. The default value is 400. gpu_freq Sets core_freq, h264_freq, isp_freq, and  v3d_freq together. The default value is 250. h264_freq Frequency of the hardware video block in MHz. The default value is 250. isp_freq Frequency of the image sensor pipeline block in MHz. The default value is 250. v3d_freq Frequency of the 3D block in MHz. The default value is 250. arm_freq_min Minimum value of arm_freq used for dynamic frequency clocking. The default value is 700. core_freq_min Minimum value of core_freq used for dynamic frequency clocking. The default value is 250. sdram_freq_min Minimum value of sdram_freq used for dynamic frequency clocking. The default value is 400.

[링크 : https://www.raspberrypi.org/documentation/configuration/config-txt.md]

[링크 : http://raspberrypi.stackexchange.com/questions/23442/raspberry-pi-b-cpu-clock-manipulation]

[링크 : http://raspberrypi.stackexchange.com/questions/41517/low-enery-consumption-kernel]

+

길어서 cpu 1,2,3은 삭제

$ cpufreq-info cpufrequtils 008: cpufreq-info (C) Dominik Brodowski 2004-2009 Report errors and bugs to cpufreq@vger.kernel.org, please. analyzing CPU 0:   driver: BCM2835 CPUFreq   CPUs which run at the same hardware frequency: 0 1 2 3   CPUs which need to have their frequency coordinated by software: 0 1 2 3   maximum transition latency: 355 us.   hardware limits: 600 MHz - 900 MHz   available frequency steps: 600 MHz, 900 MHz   available cpufreq governors: conservative, ondemand, userspace, powersave, performance   current policy: frequency should be within 600 MHz and 900 MHz.                   The governor "ondemand" may decide which speed to use                   within this range.   current CPU frequency is 600 MHz.

$ cat /boot/config.txt #uncomment to overclock the arm. 700 MHz is the default. #arm_freq=800 arm_freq_min=300

길어서 cpu 1,2,3은 삭제

$ cpufreq-info cpufrequtils 008: cpufreq-info (C) Dominik Brodowski 2004-2009 Report errors and bugs to cpufreq@vger.kernel.org, please. analyzing CPU 0:   driver: BCM2835 CPUFreq   CPUs which run at the same hardware frequency: 0 1 2 3   CPUs which need to have their frequency coordinated by software: 0 1 2 3   maximum transition latency: 355 us.   hardware limits: 300 MHz - 900 MHz   available frequency steps: 300 MHz, 900 MHz   available cpufreq governors: conservative, ondemand, userspace, powersave, performance   current policy: frequency should be within 300 MHz and 900 MHz.                   The governor "ondemand" may decide which speed to use                   within this range.   current CPU frequency is 300 MHz.   cpufreq stats: 300 MHz:16.33%, 900 MHz:83.67%  (7)

$ cat /boot/config.txt arm_freq=600 arm_freq_min=100

$ cpufreq-info cpufrequtils 008: cpufreq-info (C) Dominik Brodowski 2004-2009 Report errors and bugs to cpufreq@vger.kernel.org, please. analyzing CPU 0:   driver: BCM2835 CPUFreq   CPUs which run at the same hardware frequency: 0 1 2 3   CPUs which need to have their frequency coordinated by software: 0 1 2 3   maximum transition latency: 355 us.   hardware limits: 100.0 MHz - 600 MHz   available frequency steps: 100.0 MHz, 600 MHz   available cpufreq governors: conservative, ondemand, userspace, powersave, performance   current policy: frequency should be within 100.0 MHz and 600 MHz.                   The governor "ondemand" may decide which speed to use                   within this range.   current CPU frequency is 600 MHz.   cpufreq stats: 100.0 MHz:0.00%, 600 MHz:100.00%

테스트 해보니.. 0.04W 감소 월(30일)기준 28.8W 절약... 이라고 해야하나?

100MHz 1.70W -> 1.66W