[Server-devel] do RPi 3 B+ still need heat sinks?

[Adam Holt]

On Mon, Apr 2, 2018 at 12:36 PM, Adam Holt <holt at laptop.org> wrote:

> On Mon, Apr 2, 2018 at 10:44 AM, Adam Holt <holt at laptop.org> wrote:
>
>> 1) Recap from 2016: heatsinks on the original RPi3 CPU are not a cure-all
>> when the RPi 3 is enclosed in a case that lacks ventilation on a hot day.
>> But CPU heatsinks Do Work when taking the plastic top off the of the
>> original RPi 3.  The CPU throttling problem "immediately" goes away on such
>> hot days...bringing the temperature back down below 80C...as measured by
>> the command:
>>
>>    *vcgencmd measure_temp*
>>
>> 2) It's snowing today right outside my window, so I can't easily simulate
>> a hot summer's day -- but can others who live in hot environments report
>> back their readings above, when running the new RPi3 B+ in various
>> conditions?
>>
>>    - *With heatsink on CPU -- and without?*
>>    - *With motherboard fully enclose by a case -- and without?*
>>
>>
> My own results, with all 4 CPU's unloaded, in a chilly room:
>

 RPi 3 with-heatsink-on-CPU / RPi 3 B+ / RPi 3 B+ with-heatsink-on-CPU
44-46C / 46-48C / 45-47C case's plastic top removed (w/o wind or active
ventilation)
46-49C / 48-51C / 48-52C case's plastic top attached (contains 100+ small
holes on 1 end, allowing very little ventilation)

After I ran "*yes > /dev/null &*" 4 times, to fully load all 4 cores of the
> CPU:
>

 RPi 3 with-heatsink-on-CPU / RPi 3 B+ / RPi 3 B+ with-heatsink-on-CPU
80-82C / 70-71C / 71-72C case's plastic top removed (w/o wind or active
ventilation)
82-84C / 75-78C / 79-82C case's plastic top attached (contains 100+ small
holes on 1 end, allowing very little ventilation)


*RESULT: attaching a heatsink to the RPi 3 B+ CPU does not help.  It might
even make things a bit worse, hmm.*
In any case: this result is completely different the original RPi 3 (where
past experiments have shown that a heatsink-on-CPU greatly lowers its
temperature, When The Case Is Open!)


> CONCLUSION: the RPi 3 B+ appears to be a real winner in CPU-intensive
> conditions, even in a "wintry" conditions (room is about 15C, and it
> continues to snow right outside the window).  The RPi 3 CPU is supposed to
> self-throttle at 80C, until it just about turns itself off at 85C.  I'd
> assume the RPi 3 B+ CPU does the same?  But do not know for sure.  Thanks
> to all who can add any similar data points, in warmer climate/conditions.
>
>
> CLARIFS:  Both RPi's were running a near-final prerelease of
> Internet-in-a-Box 6.5 on Raspbian Lite to explore real-world conditions.
> I waited 10+ min in all above 8 experiments before taking "steady state"
> temp readings.  Still, fluctuations in CPU activity (and temperature)
> arise, even long after I ran "killall yes" to end the most intensive CPU
> activity.
>
>
> 3) Prelim thermal analysis of RPi 3 B+:
>>
>> https://cdn-images-1.medium.com/max/1600/1*0jU89Yu_6miI-CODBMuHAw.png
>> https://medium.com/@ghalfacree/benchmarking-the-raspberry-pi
>> -3-b-plus-44122cf3d806
>>
>> --
>>
>> <https://medium.com/@ghalfacree/benchmarking-the-raspberry-pi-3-b-plus-44122cf3d806>
>>
>> <https://medium.com/@ghalfacree/benchmarking-the-raspberry-pi-3-b-plus-44122cf3d806>
>> Unsung Heroes of OLPC, interviewed live @
>> <https://medium.com/@ghalfacree/benchmarking-the-raspberry-pi-3-b-plus-44122cf3d806>
>> http://unleashkids.org !
>>
>> --
>> Unsung Heroes of OLPC, interviewed live @ http://unleashkids.org !
>>
>
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