Vanfanel
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Raspberry Pi 3 CPU powersave feature question

Wed Jan 10, 2018 10:50 am

Hi,

As you may know, at least on the X86 world CPUs enter so-called c-states to save power when they are idle.
Hence passing "idle=poll" to the kernel config parameters disables this option (some people do it to improve system jittering).
So, do the ARM cores on a Pi3 have this feature? Can it also be disabled via the "idle=poll" kernel parameter of other parameters?

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DougieLawson
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Re: Raspberry Pi 3 CPU powersave feature question

Thu Jan 11, 2018 3:31 pm

None of the Raspberries have any power saving feature. It's not needed when it costs less than £5.00 per year to run one 24/365.
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Vanfanel
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Re: Raspberry Pi 3 CPU powersave feature question

Thu Jan 11, 2018 3:47 pm

DougieLawson wrote:
Thu Jan 11, 2018 3:31 pm
None of the Raspberries have any power saving feature. It's not needed when it costs less than £5.00 per year to run one 24/365.
Thanks, Dougie. I thought the ARM cores would have these states implemented anyway, since they are used in mobile setups, etc.

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hojnikb
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Re: Raspberry Pi 3 CPU powersave feature question

Sun Jan 14, 2018 8:52 am

DougieLawson wrote:
Thu Jan 11, 2018 3:31 pm
None of the Raspberries have any power saving feature. It's not needed when it costs less than £5.00 per year to run one 24/365.
Well, not a very good argument. You could have raspberry pi in a battery powered environment, where every W counts. Or in the case of rpi3, you could increase sustained performance by downclocking the cpu and thus having less heat to deal with.
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jahboater
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Re: Raspberry Pi 3 CPU powersave feature question

Sun Jan 14, 2018 9:17 am

hojnikb wrote:
Sun Jan 14, 2018 8:52 am
Well, not a very good argument. You could have raspberry pi in a battery powered environment, where every W counts. Or in the case of rpi3, you could increase sustained performance by downclocking the cpu and thus having less heat to deal with.
The governor does downclock the CPU's when idle.
At idle the Pi3 runs at 600Mhz, going up to 1200Mhz under load.
You can adjust either limit in /boot/config.txt

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