While conducting our internal engineering load tests of the Raspberry Pi 3 Model B, it became evident that the Raspberry Pi 3 REQUIRES heatsinks. Without them, the board will overheat and experience thermal shutdown, corrupt HDMI signal, and video corruption. SoC diode temperatures are also incorrectly reported lower than actual temperatures. A test of 4 threaded sysbench resulted in the imagery below.
We suggest active cooling for this board. At full load, it generates considerable heat and will become unstable. Once we get stock, our Raspberry Pi 3 boards will come with free heatsinks. Our kits for Raspberry Pi 3 will be actively cooled and we recommend anyone who plan to put the Pi 3 into an enclosure to have active cooling.
Aluminum has a different emissivity than the die. All measurements were taken with a calibrated contact thermalcouple probe on the top edge of the SoC.
In our passive cooled no heatsink CPU+GPU load test, the board turned off within a minute of the start of the test. This suggests that BCM2837 is indeed still a 40nm part as our 28nm Allwinner SoCs do not exhibit this problem. The temperature sensor on the BCM2837 becomes inaccurate after 80C. When the SoC has hit 100C, it is still reporting 83C. This prevents the 85C firmware throttling from kicking in.
Hopefully, the Raspberry Pi Foundation will make patches to the firmware and Linux kernel to improve the throttling mechanism and to prevent this from happening in a future Raspbian image release. We tested against the latest 2016-02-26 Raspbian image.
To replicate, run the following:
apt-get install -y sysbench && sysbench --num-threads=4 --max-requests=999999 --test=cpu run
To test the GPU, first turn on the GL driver in raspi-config. Then run:
apt-get install -y mesa-utils && glxgears
|Steady State (22C Ambient)||Active Cooling||Passive Cooling|
|No Heatsink||64C||100C (Shutdown)|