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

[James Cameron]

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?

> 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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-- 
James Cameron
http://quozl.netrek.org/