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

Tue Apr 3 17:28:31 EDT 2018

On Tue, Apr 3, 2018 at 5:01 PM, James Cameron <quozl at laptop.org> wrote:

> On Tue, Apr 03, 2018 at 10:33:12AM -0400, Adam Holt wrote:
> > On Mon, Apr 2, 2018 at 12:36 PM, Adam Holt <[1]holt at laptop.org> wrote:
> >
> >     On Mon, Apr 2, 2018 at 10:44 AM, Adam Holt <[2]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.
>
> Yes, your heatsink is no good.
>
> The B+ CPU has a heatsink or heat spreader already, that silver
> coloured bevelled structure with the black dot and Broadcom logo.
>
> What is the shape, size, and attachment method for your added
> heatsink?
>

It's the standard Canakit 7-fin aluminum heatsink shown here, attached to
the CPU with its own basic 3M self-adhesive sticker:

http://www.bestofjay.com/w/raspberry-pi-3-overclock-heat-test-flirc-case-vs-canakit-heatsink/
http://11986-presscdn-0-77.pagely.netdna-cdn.com/wp-content/uploads/2016/04/heat-sinks-installed.jpg

FWIW these same heatsinks do lower the temperature of the original RPi 3 by
many degrees IF the CPU 's under medium load AND the top of the plastic
case is removed :)

> 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+:
> >
> >         [3]https://cdn-images-1.medium.com/max/1600/1*0jU89Yu_6miI-CODB
> >         MuHAw.png
> >         [4]https://medium.com/@ghalfacree/benchmarking-the-raspberry-pi
> >         -3-b-plus-44122cf3d806
> >
> >         --
> >         [5]
> >         [6]Unsung Heroes of OLPC, interviewed live @ [7]
> http://unleashkids.org
> >         !
> >
> >         --
> >         Unsung Heroes of OLPC, interviewed live @ [8]
> http://unleashkids.org !
> >
> >
> > References:
> >
> > [1] mailto:holt at laptop.org
> > [2] mailto:holt at laptop.org
> > [3] https://cdn-images-1.medium.com/max/1600/1*0jU89Yu_6miI-
> CODBMuHAw.png
> > [4] https://medium.com/@ghalfacree/benchmarking-the-
> raspberry-pi-3-b-plus-44122cf3d806
> > [5] https://medium.com/@ghalfacree/benchmarking-the-
> raspberry-pi-3-b-plus-44122cf3d806
> > [6] https://medium.com/@ghalfacree/benchmarking-the-
> raspberry-pi-3-b-plus-44122cf3d806
> > [7] http://unleashkids.org/
> > [8] http://unleashkids.org/
>
> > _______________________________________________
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> > Server-devel at lists.laptop.org
> > http://lists.laptop.org/listinfo/server-devel
>
>
> --
> James Cameron
> http://quozl.netrek.org/
> _______________________________________________
> Server-devel mailing list
> Server-devel at lists.laptop.org
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>

-- 
Unsung Heroes of OLPC, interviewed live @ http://unleashkids.org !
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