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The Pi Foundation just announced the second iteration of the compute module, usefully called the Compute Module 3. In their press release they've dropped some fairly hand-wavey statements about the module's current draw and subsequent thermal properties:

With a few caveats, the CM3 can be used a drop-in replacement for the CM1 since they are pin compatible; the CM3 is 1mm taller, however, while the CPU can pull a lot more current from the VBAT power supply line and will generate far more heat under heavy load.

All the fun applications for these things I can think of put them in pretty tight enclosures, which isn't ideal for high temperatures. How much current does a Compute Module 3 draw during heavy load, and what temperature does it reach at that point?

  • A quick Google search of reviews doesn't through up any in-depth bench-marking. I wonder if anyone on the site has one and is willing to do some testing? – Darth Vader May 25 '17 at 15:41
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What I have seen is each CM3 will pull up to 0.5A at room temperature. The data sheet claims 3500mW on the VBAT supply (nominally 5V) which would be 0.7A.

The difference could be due to part tolerances, fudge factor on their part or my poor estimation technique (just looking over at my benchtop supply)

To load the CPU 100% I run stress -n 4 which is good enough for me, but may not fully load all the IP inside the processor.

As for thermals - the chip BCM2837 is rated to 85C but the memory is only rated to 80C. The CPU also uses DVFS so will start throttling when its internal temperature reaches 85C.

A default Raspbian installation will automagically cuts CPU clock from 1.2GHz to 600MHz when the temperature reaches 85C. This helps lower the temperature but also (obviously) impairs performance.

To manage heat thermal foam (low cost) or an aluminum heat sink (higher cost) can be used to keep it pretty cool, even without a fan.

With thermal foam and using stress -n 3 at an ambient temperature of 55C, it's possible to keep the CPU around 75-80C. That test ran for several hours without ever throttling the CPU frequency down.

For power & thermal specifications, see the CM3 datasheet: https://www.raspberrypi.org/documentation/hardware/computemodule/datasheets/rpi_DATA_CM_1p0.pdf

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Please check this link https://www.element14.com/community/docs/DOC-83880/l/does-this-compute-raspberry-pi-compute-module-3-and-io-board

It provides some information about additional power consumption and dissipation

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