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In the Start menu (you know, the fruit button at the top-left corner), I clicked shutdown. I did not unplug the USB-C power cable. The red light was still on, but I thought it was like the sleep light of a PC monitor. After leaving Pi in this state for more than one hour, I just picked it up thinking that it would be cold, but no, it was still warm. I touched the CPU and it was quite warm.

To make sure that it was not on (headless set-up, nothing was connected, not even Ethernet), I tried SSH and VNC. Both failed to connect, so I guess it was in the soft-off state.

But why is it warm? It has no battery, so it cannot be the heat from charging. All devices I have used did not generate heat when they are off, even if the power cable has been connected. So, I cannot understand. Why is it warm after more than 1 hour after being shut down? Does it do something even when it has been shutdown?

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The Pi has 3 "components" the CPU, GPIO and Video Core which are relatively independent. Even when the Pi is shutdown the Video Core continues to run, and the GPIO pins retain their state; only the CPU is not running.

(All Pi models before the Pi4 have identical GPIO and Video Core; only the CPU changed on the Pi2 and the Pi3. The Pi4 is all new.)

The 3.3V and other voltages used by the SOC are supplied by separate circuitry and will be present while ever the Pi is connected to a 5V supply.

The original Pi4 put the MxL7704 power management chip into a low power state when off - turning off the 3.3V supply and effectively totally shutting down the SoC. (I verified this by measuring the current.)

Unfortunately due to lobbying by a lot of luddites who had designed HATs that assumed 3.3V power was always available the EPROM is now configured by default to enable the MXL7704 PMIC when shut down. So you can now reboot by pulling pin 5 low.

It is possible to change this behaviour by modifying the Pi4 EEPROM. See Pi 4 Bootloader Configuration.

I have not actually bothered to change this on my Pi4, as I never shut my Pi down.

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  • Thanks. I haven't tried the thing in the linked page, but you mean that I can make Pi actually shut off by changing some bootloader settings, right? I am not using any HAT (I guess that is an attached board), so I don't need the power. – Damn Vegetables Jul 8 at 3:22
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All sorts of circuitry will be powered while power is applied even after you shut down the operating system. You would have to study the schematics for your Pi model to check which components are still powered.

I think early Pi's still used about 100 mA at 5V when shutdown.

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It's warm because it's still consuming power.

In reading your question, I initially assumed you were confused, or that shutdown from the GUI interface was somehow different from shutdown command entered at the terminal. My skepticism was based on something I read in the Raspberry Pi forum posted about a year ago (June 2019). In this post, a "Raspberry Pi Engineer" stated that power consumption in shutdown should be "about 3mA". In this same post, he also states, ""sudo poweroff" will shut down the PMIC".

Note: According to the documentation shutdown defaults to poweroff; i.e. both commands lead to the same system state.

I attempted to replicate your results on my headless RPi 4B:

My results match yours; I can confirm your observation that the RPi 4B consumes a substantial (much greater than 3 mA) amount of power after entering shutdown or poweroff mode. Further, it also seems that shutdown/poweroff does not shut down the PMIC.

To confirm this, I took some power measurements:

My power measurements:

I used an inline USB tester to make some measurements of the voltage and current being supplied to my RPi4B in these states:

  1. "Normal", low level of activity: voltage=4.99V, current draw=0.51A

  2. After sudo poweroff: voltage=5.04V, current draw=0.38A

  3. After sudo shutdown: voltage=5.04V, current draw=0.38A

And so in this case, the power decrease in shutdown/poweroff state is not substantially less than when the unit is in its "normal" (mostly idle) state. This explains why the RPi remains warm - the power dissipation in shutdown/poweroff state is ~ 1.9 watts.

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  • The other answer explains why it does not shut down so-called PMIC, whatever that is. – Damn Vegetables Jul 8 at 3:27
  • @DamnVegetables: PMIC: Power Management Integrated Circuit. I think you chose the best answer! ICYI, stay tuned to this discussion... Milliways' reference implies the default behavior can be modified to turn the PMIC off and (perhaps) reboot by pulling GLOBAL_EN to ground. If it's that simple, that opens up some new application areas. – Seamus Jul 8 at 7:03

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