Biero
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Raspberry Pi 4 overheat : why not underclocking a little ?

Wed Aug 28, 2019 2:27 pm

Hello Everyone !
I’m quiet interested in the new Raspberry pi 4, but also concerned (like a lot of people) by the heat it can generates.
I saw a lot of conversations about the good way to cool the Pi (Flirc case, fan, heatsink etc).
But I wonder if it wouldn’t be more relevant to underclock the Pi 4 ? Indeed :

- The New Pi 4 is 2 times more powerful than the old one Pi 3 => underclocking would let the Pi 4 significantly more powerful than the Pi 3 anyway
- For some applications, the underclocked Pi 4 probably still do the job perfectly (media center for example : I guess that CPU speed is not influent but GPU speed is ?)
- As the Pi 4 starts throttling after some minutes, we are probably not far from no throttling at all using little underclocking

As an example, here :
https://images.anandtech.com/doci/9878/power-big.png
https://www.anandtech.com/show/9878/the ... 8-review/3
Anandtech showed that on a Cortex A72 reducing the frequency by 15% (from 2.3 GHz to 2 GHz), the power consumption is reduced by about 30% (from 3700 mW to 2500 mW), which seems a lot.
Of course, it’s into a phone, and it’s 16 nm process instead of 28 nm process on the Pi 4. But it’s to illustrate that it seems possible to reduce a lot the heat with a small underclocking.

So, would it be possible for someone who got a Pi4 to underclock by 15 % (From 1,5 GHz to 1,3 GHz or 1,2 GHz or lower if needed), and see the temperature result in stress test ? To do so, if I'm correct, put in the config.txt :
- arm_freq=1300
- over_voltage=-1 (At first try without this option… Probably the foundation could give us the correct value to reduce voltage in a 1,3 GHz or 1,2 GHz case ?)

Thanks a lot for your comments / ideas !

Biero

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mahjongg
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Re: Raspberry Pi 4 overheat : why not underclocking a little ?

Wed Aug 28, 2019 2:38 pm

most people are only concerned about their PI4 to get too hot because the PI4 already will start to under clock when it feels the need to do so to keep its temperature below the real limit, the limit that is programmed into it.
They simply don't want it to start it under clocking.

the problem isn't that the PI becomes too hot, (there is no reason to fear it will become damaged, it will never get so dangerously hot that there is a realistic fear that that will happen, its not like a PC cpu which will burn up when you remove its heatsink) but the problem is that the PI automatically under clocks when it becomes uncomfortably hot.

also it takes just a tiny bit of airflow over the PI to take most of the heat away from it, mounting it vertically and not hinder such airflow is all that is really needed, to not to let it auto under clock.

jbudd
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Re: Raspberry Pi 4 overheat : why not underclocking a little ?

Wed Aug 28, 2019 2:40 pm

If the Pi 4 is booted up but not doing anything demanding, it does reduce the clock frequency very substantially - to 600MHz. And even so the temperature can easily reach 60°C if it's in a case.

pica200
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Re: Raspberry Pi 4 overheat : why not underclocking a little ?

Wed Aug 28, 2019 3:03 pm

As said above the fear is not heat damage but throttling. You won't get everything out of it when it can't hold the clock rate without going >80°C. I would not let it run at around 80 if it's a 24/7 Pi either but that's personal preference.

Biero
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Re: Raspberry Pi 4 overheat : why not underclocking a little ?

Wed Aug 28, 2019 3:28 pm

Well, I get your point about automatic underclocking. If I use the Pi 4 as desktop computer, I’ll probably let it manage its frequency.

But my first use will be media center. Currently I have a Pi 2 and it’s wonderfull : it’s switched on 24h a day, it’s always immediately available. And it does not generate heat which is a good thing as it’s inside a closed furniture => I like the idea that the temperature does not rise inside.

Going to a Pi 4 would add benefits (H265, USB powered Hard Drive, Gigabit…). But :
- Even in idle condition it seems that the heat is noticeable
- In use (nearly whatever usage), I saw lots of feed-back saying that the CPU reach 80°C quickly and stay there underclocking automatically.
So, I understand there is no damaging problem to fear. But also, if heat can be reduced in a media player usage switched on 24h a day (inside a closed furniture…), why not ? That’s why I thought in underclocking. It can be both at max and min speed by the way :
- arm_freq=1300 (instead of 1500) (In fact it could be less than 1300… I just want the Pi to handle H265 flow => If 1000 is OK, then perfect !)
- arm_freq_min = 400 (for example ? instead of 600 if I’m correct ?)

I hope you got my point for media player usage, switched on 24h a day, with minimum heat. Ideally I would need a Pi2 with H265 capability :) ! I understand there is no reliability problem with the Pi 4, but if it can be optimized in media player usage, it could be useful !

Biero
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Re: Raspberry Pi 4 overheat : why not underclocking a little ?

Wed Aug 28, 2019 3:42 pm

Obs : My idea is related to media player usage, but I suppose that other usages could benefit for the same heat reduction (NAS, Automation...) as they don't need a lot of power. (They could use older version on Pi also... But I guess sometimes users could be intereseted by Pi 4 new functionalities)

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Re: Raspberry Pi 4 overheat : why not underclocking a little ?

Wed Aug 28, 2019 3:53 pm

One of the problems is not really the top frequency I think it's the overvoltage plus possible GPU clock otherwise the CPU sits at 600 megahertz
Even if you leave everything stock. bored in the case without the lid on sits at about 60 C 63 c idle. If anything maybe even overclocking would be better because at a higher frequency it's going to get things done quicker and get the processor back to 600 megahertz quicker. The heat issue is a real thing, maybe a new case could be released that allows the 4B to sit vertically and naturally convection cool.
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pica200
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Re: Raspberry Pi 4 overheat : why not underclocking a little ?

Wed Aug 28, 2019 4:21 pm

Then try it and report back. You will probably need to underclock + undervolt quite a bit to get temps down.

ejolson
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Re: Raspberry Pi 4 overheat : why not underclocking a little ?

Wed Aug 28, 2019 4:28 pm

Biero wrote:
Wed Aug 28, 2019 3:28 pm
Well, I get your point about automatic underclocking. If I use the Pi 4 as desktop computer, I’ll probably let it manage its frequency.

But my first use will be media center. Currently I have a Pi 2 and it’s wonderfull : it’s switched on 24h a day, it’s always immediately available. And it does not generate heat which is a good thing as it’s inside a closed furniture => I like the idea that the temperature does not rise inside.

Going to a Pi 4 would add benefits (H265, USB powered Hard Drive, Gigabit…). But :
- Even in idle condition it seems that the heat is noticeable
- In use (nearly whatever usage), I saw lots of feed-back saying that the CPU reach 80°C quickly and stay there underclocking automatically.
So, I understand there is no damaging problem to fear. But also, if heat can be reduced in a media player usage switched on 24h a day (inside a closed furniture…), why not ? That’s why I thought in underclocking. It can be both at max and min speed by the way :
- arm_freq=1300 (instead of 1500) (In fact it could be less than 1300… I just want the Pi to handle H265 flow => If 1000 is OK, then perfect !)
- arm_freq_min = 400 (for example ? instead of 600 if I’m correct ?)

I hope you got my point for media player usage, switched on 24h a day, with minimum heat. Ideally I would need a Pi2 with H265 capability :) ! I understand there is no reliability problem with the Pi 4, but if it can be optimized in media player usage, it could be useful !
Last year Matt Dillon posted results on underclocking a Ryzen Threadripper system, particularly the memory, that focused on optimizing the total amount of electrical energy used to build a large software project. My recollection is that the results were interesting in that neither the highest nor lowest clock speeds achieved optimal efficiency, but some intermediate setting.

Is it possible for some loads that the Pi initially runs at the highest speed and then throttles down to the lowest? If so, that may pick up two extreme modes of operation both of which are inefficient from a get the work done using the least amount of energy point of view.

I suspect the optimally green clock speed depends on the nature of the work which needs to be finished. At the same time, setting up a media player seems common enough that guidelines for that task may have widespread application.

jbudd
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Re: Raspberry Pi 4 overheat : why not underclocking a little ?

Wed Aug 28, 2019 5:33 pm

Is it possible for some loads that the Pi initially runs at the highest speed and then throttles down to the lowest? If so, that may pick up two extreme modes of operation both of which are inefficient from a get the work done using the least amount of energy point of view.
Maybe the people who designed it have already optimised the peak and idle speeds?

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Re: Raspberry Pi 4 overheat : why not underclocking a little ?

Wed Aug 28, 2019 5:45 pm

jbudd wrote:
Wed Aug 28, 2019 5:33 pm
Is it possible for some loads that the Pi initially runs at the highest speed and then throttles down to the lowest? If so, that may pick up two extreme modes of operation both of which are inefficient from a get the work done using the least amount of energy point of view.
Maybe the people who designed it have already optimised the peak and idle speeds?
Indeed, although we are constantly looking for better settings. The main problem is lack of PLL's and PLL dividers on the SoC to provide all the different constant clocks required to run the system, but still allow the governor to raise and lower the CPU clock as necessary.

In my testing with lower clock rates, I did see slight lowering of temperatures. Use the config.txt entry for min processor and max processor frequencies.
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Moonmarch
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Re: Raspberry Pi 4 overheat : why not underclocking a little ?

Wed Aug 28, 2019 6:05 pm

A new software update should lower the clock speed to reduce the computer temperature this is important for people who do not monitor computer temperatures, which is the reason why the computer not reaching max load temperature is necessary if the computer does overheat one day, how do you know if the person using the computer knows how to cool down the computer, watching videos about adding heat sinks to the RPI computer the square heat sinks are not very effective at lowering computer temperatures which means you will not be able to passively cool down the RPI computer without buying a aluminum case or use internal fan, here is a link to the RPI aluminum case video:

Flirc Case For The Raspberry Pi 4 - The Best Pi4 Case! - First Look And Thermal Testing:
https://youtu.be/vkLr08K0c1E

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Re: Raspberry Pi 4 overheat : why not underclocking a little ?

Wed Aug 28, 2019 6:23 pm

Moonmarch wrote:
Wed Aug 28, 2019 6:05 pm
A new software update should lower the clock speed to reduce the computer temperature this is important for people who do not monitor computer temperatures, which is the reason why the computer not reaching max load temperature is necessary if the computer does overheat one day, how do you know if the person using the computer knows how to cool down the computer, watching videos about adding heat sinks to the RPI computer the square heat sinks are not very effective at lowering computer temperatures which means you will not be able to passively cool down the RPI computer without buying a aluminum case or use internal fan, here is a link to the RPI aluminum case video:

Flirc Case For The Raspberry Pi 4 - The Best Pi4 Case! - First Look And Thermal Testing:
https://youtu.be/vkLr08K0c1E
Really not sure what you are saying.

Why is a new software update necessary, and for what reason? The user does not need to know how to cool the device, it does it itself, automatically.
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Biero
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Re: Raspberry Pi 4 overheat : why not underclocking a little ?

Wed Aug 28, 2019 8:56 pm

Hello Jamesh,

A previous comments was quite wright : in fact I (we ?) would be glad to have guidelines to built media player using Pi 4. => To get values for CPU frequency and GPU frequency that will limit heat production as much as possible, keeping media player functionalities (H265 decoding in particular)

To illustrate, in my case I would be happy with a "Pi 2 with H265 decoding capability". A Pi 2 has 4 Cortex A7 running at 900 MHz and Libreelec reactivity is perfect !
The Pi4 has 4 Cortex A72 and if I'm correct, the Pi 4 throttling frequency is 600 MHz ? And 600 MHz on cortex A72 performance is maybe close to 900 MHz cortex A7 ?

So, exagerating a little, if I limit the CPU frequency to 600 MHz, the SOC temperature may never go well beyond idle temperature (60°C ?).
Would you be able to tell us in that case if H265 decoding capability is still OK ? (with arm_freq=600 )

Regarding GPU, I would imagine that H265 decoding capability is linked to GPU frequency ? Or not ? If not, if may be possible to lower GPU frequency ? (gpu_freq=400 for example) ?
On Pi 4, is "h264_freq" parameter responsible for both H264 and H265 decoding ? if yes, maybe the solution is to get adequate values for gpu_freq ; core_freq and h264_freq parameter... Although it sounds comlpicated... But maybe in the future with complete "Pi 4 media player guidelines" ?

Thanks a lot !

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Re: Raspberry Pi 4 overheat : why not underclocking a little ?

Thu Aug 29, 2019 1:08 am

When the RPI computers receive the next update I don't know what will be updated specifically the next update can include lower stock clock speeds to prevent the computer from reaching max temperature, which means the RPI4 computer will then be advertised with different base clock speeds instead of the 1.5 GHz, same CPU different speeds still faster than the RPI3 computers the RPI4 computers can be overclocked to 2 GHz for people who know how to overclock, when you overclock the CPU the CPU temperature increases when you reduce the CPU clock speed the CPU the temperature should decrease, here is a video about overclocking the Raspberry Pi 3:

Raspberry Pi 3: Overclocking:
https://youtu.be/3B3AnuOmRcQ

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Re: Raspberry Pi 4 overheat : why not underclocking a little ?

Thu Aug 29, 2019 1:33 am

There are a variety of options available for lowering thermals on the Pi4.
The first one, will be to lower idle voltage and clocks.
Stock, the Pi runs at 400-500Mhz I believe. You can easily lower this to 250Mhz, and lower the idle voltage as well:

Code: Select all

arm_freq_min=250
over_voltage_min=-3
Where '-3' is a setting you'd have to find where your Pi runs most stable.
This setting will allow your Pi to run a bit cooler during idle (which usually is the state the CPU is found most in).
Aside from that, you can lower the Pi's 1,5Ghz to 1,45Ghz, and roll down the voltage to the lowest point.
But most of your cooling you're probably going to get by adjusting the idle.

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Re: Raspberry Pi 4 overheat : why not underclocking a little ?

Thu Aug 29, 2019 3:38 am

My attempt to under-volt/under-clock did not success yet. See the post:

https://www.raspberrypi.org/forums/view ... 9#p1527629

If anyone got some effective under-clock/under-volt settings, it will be nice to share.

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Re: Raspberry Pi 4 overheat : why not underclocking a little ?

Thu Aug 29, 2019 5:18 am

I recall some people reporting that after underclocking, their Pi ran 2-3°C cooler... Hardly worth it if you've got it in a heat trap small plastic enclosure.

If you want to try it though, here's a starting point.
https://www.raspberrypi.org/forums/view ... 6#p1526216
Although it looks like you may have already tried that.

Note that you will need to ensure you are fully apt-get updated as there were some fixes shortly after release that are necessary to allow undervolting and other config changes.
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Mikael
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Re: Raspberry Pi 4 overheat : why not underclocking a little ?

Thu Aug 29, 2019 11:24 am

My guess is that the Cortex-A72 cores generate only a very small amount of the heat at idle. Therefore, trying to underclock and undervolt them further will have very limited effect. It's likely that any meaningful idle power consumption reductions will need to come from the RPF in the form of firmware updates with improved clock frequency and state management.

Clock frequency and voltage should make a decent difference when the CPU is doing actual work, though.

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Re: Raspberry Pi 4 overheat : why not underclocking a little ?

Thu Aug 29, 2019 2:50 pm

In the media center application you have three conflicting issues:

1) Environment - closed cabinet with other heat sources, which may raise local ambient significantly above "room" temperature.

2) Always on, appliance like functionality, plus relatively high loads when streaming

3) Noise sensitivity - either fanless or need quiet fans

Given 1 & 2, underclocking is not going to do much. You really need an active heat transfer solution. A large heatsink may help, but it is likely going to heat soak eventually and it is not going to be as effective if ambient temps get too high. If your media setup is "free air" and you can place it low enough to get room air temps, natural convection cooling with a heat sink may get you enough cooling. Further encasing the Pi in a small box with very restricted air flow will make matters much worse.

I know I had to go with a forced air system with my last media center (equipement was all built in to the wall) to remove enough heat.

ninjapi
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Re: Raspberry Pi 4 overheat : why not underclocking a little ?

Thu Aug 29, 2019 6:03 pm

the easiest way to get it to automatically underclock itself is to put it in the official case.

ProDigit
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Re: Raspberry Pi 4 overheat : why not underclocking a little ?

Fri Aug 30, 2019 4:46 am

I'm all for those massive passive heat sinks.
For small jobs they do a good job.
If you're running your CPU for longer duration at 25% or more load, you'll need to go with an active cooling solution (fan).

If you're mostly running the Pi passive (eg: terminal, chat server, bit torrent client, media server, or other small programs from terminal that only require small load times), I would go with a huge passive heat sink. One of those that's almost the size of the pi itself.
They act like a heat buffer (remove heat efficiently from the CPU for short duration, until the sink is saturated); but also need a little longer to cool down.

Moonmarch
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Re: Raspberry Pi 4 overheat : why not underclocking a little ?

Fri Aug 30, 2019 8:32 am

To adjust the clock speeds on a computer you would need access to the motherboard bios after watching several videos about overclocking Intel computers some Intel computers are not required to be unlocked to overclock the computer if you have a certain bios version of the motherboard, if the clock speeds on the RPI computer are controlled with the /boot/config.txt file I will say the config.txt file is not a bios, and certain parameters are controllable using the config.txt file which means all additional parameters are controlled using the motherboard bios not config.txt.

Overall I don'y actually own a RPI4 I'm still on the RPI3, people need to take into consideration the RPI4 was released in July if people are not comfortable with the RPI4 the RPI3 is still completely usable if you are using Raspbian Buster OS, and the RPI3 does not have this overheating problem.

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Re: Raspberry Pi 4 overheat : why not underclocking a little ?

Fri Aug 30, 2019 8:47 am

ProDigit wrote:
Fri Aug 30, 2019 4:46 am
If you're mostly running the Pi passive (eg: terminal, chat server, bit torrent client, media server, or other small programs from terminal that only require small load times), I would go with a huge passive heat sink. One of those that's almost the size of the pi itself.
They act like a heat buffer (remove heat efficiently from the CPU for short duration, until the sink is saturated); but also need a little longer to cool down.
For those use cases I wouldn't even bother with extra cooling.

Larger heat sinks also have larger surface area, so they sink more AND can cool faster, especially if they are finned.
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Re: Raspberry Pi 4 overheat : why not underclocking a little ?

Fri Aug 30, 2019 9:30 am

ProDigit wrote:
Fri Aug 30, 2019 4:46 am
I'm all for those massive passive heat sinks.
For small jobs they do a good job.
If you're running your CPU for longer duration at 25% or more load, you'll need to go with an active cooling solution (fan).
You don't. At stock clocks the heatsink cases floating around will remove enough heat to stay way under 80°C. In my case it was 68°C and 59 under absolutely full load using cpuburna53. Former was with way higher ambient temp hence why the increse. If you overclock a fan (plus heatsink if you want) will do the job.

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