MasaPI
Posts: 7
Joined: Mon Jun 10, 2019 3:24 pm

[RBPI3B]Different CPU speed settings?

Mon Jun 10, 2019 3:52 pm

Hello everyone,

this is my first thread here so please, i'm not good at this and my english isn't the best, but i try.
Thanks.

I want that my RbPi3 model B runs slower with no load and a bit faster with load.
At the internet, i found something to change it a bit but it doesn't satisfy me.

At the moment i set the cpu speed to a min of 300MHz and max at 1000MHz.
With the config.txt in the /boot directory i set it with arm_freq_min=300 and arm_freq=1000.
I can work at 300MHz because i don't need it so fast but when i'm not currently working on it, it falls below ~20% load.
Under ~20% i want that the pi runs slower, i think of 100Mhz.
I want to save some power and temperature with that since i need it running 24H for testing and other things.
The standart was 1.2GHz.

If someone has a idea/answeres i'm open for it.


MasaPI

choubidou13
Posts: 1
Joined: Mon Jun 10, 2019 8:26 pm

Re: [RBPI3B]Different CPU speed settings?

Mon Jun 10, 2019 8:48 pm

unless the room temp is at 50° or your pi is locked by never_over_voltage, you shouldnt lower the idle frequency. no harm will be done if you do so but its pointless as the pi doesnt automatically lower the cpu voltage under 600mhz.

i once tested the voltages at different frequencies : (rpi 3b+) these values may not be exact, they are from memory :
0-600 mhz = 1.2v
650-1000 = 1.2232v
1050-1200 = 1.23323v
1250+ = 1.3323v

if your pi allows you to overvolt it, you could probably undervolt it by using these variables in config.txt
(dont forget the minus, feel free to decrease if you want)
over_voltage=-1
over_voltage_min=-1 #dont use force_turbo if you use this if you care about the warranty

Moonmarch
Posts: 94
Joined: Thu Mar 07, 2019 1:34 am

Re: [RBPI3B]Different CPU speed settings?

Tue Jun 11, 2019 7:54 am

Change the CPU governor setting, search for how to change the CPU governor, the default setting is ondemand, there are various settings to choose from, to set clock speeds for the CPU you can always try trial and error editing the config.txt file, there is a guide on how to adjust clock settings in the RPI quick start guide, click on configuration, to see the current CPU clock speed, use this command in the terminal:

Code: Select all

cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq
You can use panel applets to monitor CPU speed or CPU temperature on the Raspbian desktop, right click on the task bar, then Add/Remove Panel Items.

MasaPI
Posts: 7
Joined: Mon Jun 10, 2019 3:24 pm

Re: [RBPI3B]Different CPU speed settings?

Tue Jun 11, 2019 8:09 am

Hello choubidou13,

my room temp ist sometimes above 28°C but nothing what the pi can‘t handle.
I use them with a case, what block more of less some airflow for passiv cooling.
I look for some self ?sticking? pads, so that i can put a cooler on. Not a big deal.

How i said, the standart speed was 1.2GHz of my RbPI3B. I decreased to 1GHz to make ist saver to run in these rooms where he is.

And yes (i think) i can overvolt them. But i don‘t do it.

I will try the settings for 0-600MHz and 650-1000MHz.

I don‘t want to overclock it, so i don‘t use the foce_turbo option XD.


Thanks

MasaPI

MasaPI
Posts: 7
Joined: Mon Jun 10, 2019 3:24 pm

Re: [RBPI3B]Different CPU speed settings?

Tue Jun 11, 2019 8:30 am

Hello Moonmarch,

so there is a way to switch between 3 different speed settings?
I only find it with 2 speeds.(min and max speed)

I use a other version from the HTop program, it can show the temp and the freq.

I try to find that


Thanks,

MasaPI

MasaPI
Posts: 7
Joined: Mon Jun 10, 2019 3:24 pm

RE:[RBPI3B]Different CPU speed settings?

Tue Jun 11, 2019 1:29 pm

Hello,

i have some updates to it, since i'm unable to put some dynamics on the cpu speed settings.

I'm currently running my Pi3b with 100-600Mhz on over_voltage=-4 (~1,29V says vcgencmd) and saved around 6-9°C depending on load.

It is not much but it runs now better for me. HTop says that i have a load between 5-15% and with that speed it's ok. I save some power and temp, everything what i wanted.

Thanks for the idea with the governor, it helps a bit to understand it more.

MasaPI

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