SuperJojo2001 wrote: ↑
Tue Nov 14, 2017 6:48 pm
Sergey RS Russia wrote: ↑
Wed Nov 08, 2017 1:26 pm
we tested Rpi3 and Rpi2 for industrial temperature range. Let you see our article https://habrahabr.ru/post/318486/
During these tests RPi 3 boards started and worked in temperature range from -35℃ to +90℃, RPi 2 – from -45℃ to +106℃. These ranges are close to industrial grade electronic components -40℃…+85℃ on the boards.
Sergey, RS Russia
Sergey, nice job indeed. But you know that the Pi 3 CPU starts throttling its clock frequency from 1.2GHz down to 600Mhz in case the CPU core temperature passes the value 80°C. At 85°C core you just have 600 Mhz left only. So even if the pi boards are running fine under such high temps, the software timings and behaviour are becoming unpredicable and this is a thing you can never ever sell to the industrial market. Pi 3 with sysbench loading the CPU by 100% reaches 80°C at room temperature already. So think of an application on your desk running fine and then you put it into an installation cabinet with higher temps inside and then it starts running slower and slower. I wouldn't.
If your code starts to run incorrectly when the CPU throttles, then you need to rewrite your code. All Linux clocks should continue to run correctly when the CPU throttles. If you are relying on non-clock related software loops for timing, that is bad code since it is also affected by caching and pipelining, so could vary even under normal conditions.
There are some exceptions - I think the I2C may suffer since its clock is linked to the CPU clock. Of course, you can get round all these issues by forcing the CPU to its lowest speed at all times.
Basically, unless you are using a peripheral that is affected by CPU clock speed, you will have no problems with a standard installation, providing your code still runs fast enough at 600Mhz. Which should cover most industrial situations - 4 cores at 600Mhz is a lot of processing power.
Also worth noting, that all the SBC that compete with Pi also throttle their CPU's if they overheat. As do current x86 devices I believe.
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
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