Cannot convince my Raspi to overclock

5 posts
by joshmosh » Fri Nov 02, 2012 1:24 pm
sofar, my Raspi (Rev. A, latest stable Raspbian with all updates, latest raspi-config version) works very well, usually 24 hrs per day.
Since I want to use it as media center, I think that some overclocking is required to give it more muscles.
So, I used raspi-config to set overclocking to high.
This was acknowledged. When I checked config.txt, I saw that arm_freq was set to 950 Mhz.

Reboot. Checked config.txt again: 950 Mhz, but cat /proc/cpuinfo said that arm clock is at 697.95, which is a far cry from 950.

Can someone please help me ? Did I something wrong or did I miss anything ?

BTW a call of /opt/vc/bin/vcgencmd measure_clocks arm shows 7000000
So overclock parameter in config.txt did not have any effect :-(

Thank you very much in advance for your help

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by dom » Fri Nov 02, 2012 1:32 pm
/proc/cpuinfo value is calculated at start of boot, before cpu_freq driver has started, so will always give ~700.
measure_clocks will give the correct answer, but note the overclock is dynamic it only boosts the speed when busy.
You'll need to ensure the Pi is busy when you measure it.
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by RaTTuS » Fri Nov 02, 2012 1:35 pm
put the system under load then then
cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq
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by joshmosh » Sat Nov 03, 2012 5:34 am
Stupid me !
Of course, if the cpu is idle, then clock rate is brought down ...
Is this also true for the voltage ? In "High" mode, overvolt is set to two.
My guess is, that - speaking in simple terms - if there is nothing to do, the "normal" mode is active and only if there is a requirement for processing power, the "high" mode will be activated. Right ?

Thank you for pointing me in the right direction. I will check that later today and give the result here.

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by joshmosh » Sat Nov 03, 2012 6:42 am
Surprise surprise,
after having started an endless loop, clock went up to 950 Mhz :D

Thanks a lot and please excuse my stupidity :oops:

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