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Where is laptop-mode-tools minimal CPU clock set?
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lednakashim
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PostPosted: Mon Aug 27, 2012 10:19 am    Post subject: Where is laptop-mode-tools minimal CPU clock set? Reply with quote

I have a Intel core i3 laptop, but I don't have an air-conditioner and the ambient temperature is in the high 90s. In this kind of weather, all I can do is watch silent live video streams of dolphins remotely encoded into text via VLC. Sometimes life is hard.

The dream is to under-clock my CPU. This will solve my problems. I don't have cpufreqd installed.

What I have
cat /proc/cpuinfo | grep "MHz"
cpu MHz : 931.000
cpu MHz : 931.000
cpu MHz : 931.000
cpu MHz : 931.000

What I want
cat /proc/cpuinfo | grep "MHz"
cpu MHz : 400.000
cpu MHz : 400.000
cpu MHz : 400.000
cpu MHz : 400.000

Why did my computer choose 931 mhz? This appears to be 40% of my clock.
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WorBlux
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PostPosted: Tue Aug 28, 2012 4:07 am    Post subject: Re: Where is laptop-mode-tools minimal CPU clock set? Reply with quote

lednakashim wrote:
I have a Intel core i3 laptop, but I don't have an air-conditioner and the ambient temperature is in the high 90s. In this kind of weather, all I can do is watch silent live video streams of dolphins remotely encoded into text via VLC. Sometimes life is hard.

The dream is to under-clock my CPU. This will solve my problems. I don't have cpufreqd installed.

What I have
cat /proc/cpuinfo | grep "MHz"
cpu MHz : 931.000
cpu MHz : 931.000
cpu MHz : 931.000
cpu MHz : 931.000

What I want
cat /proc/cpuinfo | grep "MHz"
cpu MHz : 400.000
cpu MHz : 400.000
cpu MHz : 400.000
cpu MHz : 400.000

Why did my computer choose 931 mhz? This appears to be 40% of my clock.


You can only drop the voltage so far before thing start messing up.

You can also make the powersave the default governor when you configure and compile the kernel.

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

shed some light on things

echo "powersave" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
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BillWho
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PostPosted: Tue Aug 28, 2012 5:48 pm    Post subject: Reply with quote

lednakashim,

I have an i3 laptop and found that the on demand governor ran cooler than the powersave.
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depontius
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PostPosted: Wed Aug 29, 2012 12:54 pm    Post subject: Reply with quote

BillWho wrote:

I have an i3 laptop and found that the on demand governor ran cooler than the powersave.


Just a comment on this... I'm assuming you're building a tickless kernel, and with the ondemand governor the system will "race to sleep", potentially saving more power than the powersave governor would. It really depends on what you're doing.

I believe I once read that ondemand and "race to sleep" was simply the best way to go for power savings.
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BillWho
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PostPosted: Wed Aug 29, 2012 8:26 pm    Post subject: Reply with quote

depontius wrote:
I believe I once read that ondemand and "race to sleep" was simply the best way to go for power savings.

Yep, I ran across a blog somewhere that recommended that setup rather than using powersave and it does appear to be working.

With powersave, the temp was running high 40's to low 50's when sitting idle for 5 to 10 minutes. Since I switched to ondemand, it ranges high 30's to low 40's under the same conditions.
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Since installing gentoo, my life has become one long emerge :)
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