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I've seen the announcement of the new Raspberry 3 but didn't find any info regarding power consumption and heating.

A 1.2 Ghz 64-bit CPU is great but does it draw a lot more power? Shall heat be an issue with small cases with the Rpi3?

I've read that 2.5A are now needed but I've read contradictory infos on the subject: that 2.5A is only if you plan to run power-hungry USB devices.

So how much more power does this draw and is it a concern at all?

Cedric Martin
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2 Answers2

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There's a short piece that includes Pi 3 benchmarks over at the PiMoroni blog.

All of the benchmarks below were carried out with just a USB keyboard and mouse connected with power supplied from the official Raspberry Pi Power Supply, with the exception of the WiFi dongle test in which the USB WiFi dongle was also connected. The Pis were naked, i.e. not in a Pibow, except for the onboard WiFi in Pibow test.

...

The benchmark we used here was Sysbench, computing primes up to 20,000. This is a heavily CPU bound test and, as such, ideal for comparing the [Pi Zero, Pi 2 and Pi 3] SoCs without side-effects from the memory or GPU.

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Current was measured with an inline USB current and voltage meter. The built-in Wireless LAN and Bluetooth and the more powerful processor mean that the Raspberry Pi 3 draws about twice the current of its predecessor when under heavy CPU load (750mA vs 360mA).

Chart showing comparison of Pi current usage

Update

...and there's a second, similarly short, piece on Pi 3 benchmarks on the MagPi site:

You can’t get extra performance without a few sacrifices. The Pi 3 draws the most power of the test group, but its extra performance means it spends more time at idle. Those looking for maximum battery life should look at the Model A+ or the Pi Zero as an alternative.

Chart showing power consumption of various Pi models

goobering
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When shutting down the HDMI and USB on the Pi3, the current drops to 160 milliAmps. In my tests, this was roughly 200 milliAmps on the Pi2. Thus, shutting down hardware (if you don't need it), can be a huge energy saver.

Update: Use this command to turn HDMI off: /opt/vc/bin/tvservice -o And this command to turn it on: /opt/vc/bin/tvservice -p

Use this command to turn USB off entirely: echo 0x0 > /sys/devices/platform/soc/3f980000.usb/buspower and this to turn it on: echo 0x1 > /sys/devices/platform/soc/3f980000.usb/buspower

Other measures which can greatly reduce power consumption:

  • Anything which uses the SD. So removing rsyslog might be useful.
  • A WiFi connection to a network. Althought I haven't been able to turn wifi off entirely, being connected to a WiFi network makes the Pi3 receive broadcast messages. This consumes more power than being just standby. So turn shut wifi down using ifdown wlan0 and turn it on using ifup wlan0 when you need it. Reduce even more power by not using DHCP every time you turn WiFi on.
  • Anything which makes the cores' frequency increase, by increasing the load.
Roel Baardman
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