Full review and tests available on the RPi forum:
https://www.raspberrypi.org/forums/view ... 4#p1056034
The Cogent.design Raspberry Pi 3 case is a heatsink + metal case, built into one complete and gorgeous unit: The heatsink design is built into the top section of the case:
This basically turns the whole case, into one giant heat dissipating goddess of a heatsink.
How does it perform as case?
- Its a heatsink and case, all built into one.
- Although the CPU will transfer all heat to the case, other components will heat up. This has been thought out well in the case design and features various slots and holes for air ventilation
- The metal finish on the exterior of the case is exceptional, with a glistening brushed finish and no sharp edges, high quality craftsmanship throughout and it shows.
- The thickness of the metal is roughly 3mm thick, its extremely high quality and exceptionally strong.
- There is also a satisfying weight to the case, it feels like its built to last.
- The case is provided with 4 adhesive, soft gel feet pads to prevent slip.
- There is only 2 parts to the case, a top and bottom.
- Both the top and bottom parts of the case, appear to be created from a single mold with no additional welding.
- Also doubles up as a hand warmer.
- There is no access to GPIO built into the case design. The top section would need to be removed for access.
How does it perform as a heatsink?
When we consider the heat will be dissipated through the whole case, with a large surface area, one should expect great results.
Lets run some CPU stress tests:
I ran two Raspberry Pi 3's at the same time, one with the Cogent.design case, and the other with a standard case. The stress tests consisted of a 8 thread CPU burn. The reason for using 8 threads is to ensure CPU overheads occur, maximizing the stress on the CPU and heat generated.
The test is run for 10 minutes using the following commands:
Stress test results:
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apt-get install -y stress stress -c $(( $(nproc --all) * 2 )) -t 600 & while (( $(ps aux | grep -ci -m1 '[s]tress') )); do echo -e "$(date) | $(( $(cat /sys/class/thermal/thermal_zone0/temp) / 1000 ))'c"; sleep 1; done
- Idle temps:
- Cogent.design Case = 35'c
- Stock case = 48'c
- Max temps reached from stress test:
- Cogent.design Case = 55'c
- Stock case = 82'c
RPi thermal throttling at 80'c, reducing CPU clocks:
We also need to consider the stock RPi and case, reached 80'c after only 1 minute and 30 seconds into the test. When a RPi reaches 80'c, thermal throttling is automatically kicked in. This reduced the RPi clocks from 1200mhz to 800mhz in an attempt to automatically lower the heat and prevent damage to the SoC.
So, although your RPi is a 1.2ghz capable, after 1 minute and 30 seconds of full load, its most likely limited to 800mhz and the high heat, reducing the life expectancy of the SoC.
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root@DietPi:~# vcgencmd measure_clock arm frequency(45)=884002000
With the Cogent.design heatsink and case, our RPi ran at 1200mhz, at all times.
Step 1: Clean the BCM chip:
We must remove all residue that is present on the BCM chip:
- Grab your girlfriends nail varnish remover and some cotton wool buds.
- Place a small amount of the nail varnish on the cotton wool bud.
- Gently rub the BCM chip with the bud, until all reside is removed.
- Dry the BCM chip by using a clean cotton wool bud to remove all remaining nail varnish.
This is required to give maximum heat dissipation efficiency through both surfaces:
NOTE: Although I was provided with a thermal compound, I decided to use a Akasa thermal adhesive pad instead as I want a permanent attachment. Step 3: Complete the case build:
It is critical to get a flush alignment.
- Put the Raspberry Pi on the bottom section of the case. Check its aligned correctly and seated well.
- Line up the top section of the case and gently place it on top of the bottom section.
- Gently press the bottom and top section together and ensure its flush.
- Now you can insert the screws and fix it into place.