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Comment by moffkalast | Hacker News Reader

Alright so 27W with heavy peripheral draw then? But 12 W still means it'll be drawing 2.4 amps instead of 1.6 when a random process decides to 100% it. I guess we can always underclock it.

The real unanswered question is, does it finally have a damn sleep mode so it can save power when idle.

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Jeff Geerling measured 1.8W idle power draw.

Based on my experience with previous Pis, I bet you’ll be able to drop that even further by turning off unused board components at boot time.

True, I've gotten Pi 4s pretty low (< 1W), disabling the LEDs, Ethernet, HDMI, and USB controller, but it's never gonna equal a proper suspend.

How did you disable the LED? I mean I can disable LEDs via /proc but not in config.txt correct?

Add

    # Disable Power LED after boot
    dtparam=pwr_led_activelow=off
    # Disable SD card activity led
    dtparam=act_led_trigger=none
    dtparam=act_led_activelow=off
    # Disable the ethernet LEDs - these are Pi4 specific values.
    # Look in the docs for the values for other Pi boards.
    dtparam=eth_led0=4
    dtparam=eth_led1=4

to /boot/config.txt

Thank you!

It appears to depend on firmware or kernel but for recent kernels (recent 6.1 or 6.2) activelow is no longer necessary [1]. It seems to work on CM4.

PS: my bad I disabled the LEDs via /sys not /proc previously:

> # for i in /sys/class/leds/*; do echo 0 > "$i/brightness"; done

[1] https://github.com/raspberrypi/firmware/issues/1742

I've had this drive me crazy.

The required lines were different between the Pi 2 and Pi 4 I was using at the time, and the documentation was not updated (or I'd found old docs).

An exercise in trial and error.

1W is honestly not that great, though. A smartphone will do 10x that out of the box, and still pling for Facebook notifications.

A smartphone has two entirely separate computers in it, the one that runs Android or iOS, and the baseband controller. The latter is built to be very power-efficient while waiting for a radio signal. It will wake up the dormant application OS computer when a push notification comes in.

The same likely can be built on top of an RPi, using, say, wake-on-LAN signaling, or some GPIO as an interrupt source. You'll have to suspend your OS while idle for a prolonged time though.

> The real unanswered question is, does it finally have a damn sleep mode so it can save power when idle.

I dream of DIY'ing a laptop, and RPi looks like a great platform for prototyping that... until you realize there's just no sensible way to put it to sleep. Hibernate + aggressive boot time optimization?

You know it's funny, my current laptop has a weird firmware bug (certified Asus moment) where it refuses to go into sleep mode. If sleep is triggered by any OS it will straight up just shut down completely. I've lost some work the first few times I used it out of habit.

Eventually though it didn't turn out to be much of an issue, SSDs boot real fast these days anyway and I can just do a full power cycle.

Meanwhile I'm genuinely annoyed that my Thinkpad takes a second or two longer to wake up from sleep than my Mac ;)

I read that the "PC style" power button allows both soft and hard shutdown, so I suppose suspend and hibernate come into the picture as well. It's mostly a matter of OS support, the firmware seems to be there.

According to Jeff Geerling the Pi 5 doesn't support suspend in firmware, altough it might be possible with an update.

> soft and hard shutdown

My reading of that was:

"soft" = trigger an orderly OS shutdown, the same as if you executed `shutdown now` on the command line.

"hard" = cut power immediately, as if you just unplugged the power cable.

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