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Comment by up6w6 | Hacker News Reader

Talking about optimizations for raspberry pi, does anyone knows if there is any low power mode configuration available ? I've always been fascinated by how smartphones can stay like one/two days in idle while a raspberry pi can't stand 10 hours with a similar battery.

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The Raspberry Pi is based on an SOC from Broadcom that was derived from SOCs designed for Set top box and Over The Top box products (i.e. Roku, AppleTV, etc.).

The Beaglebone is based on an SOC from TI that was designed for (at the time High End) Smartphones. Therefore it supports much lower power consumption and idle modes.

The BCM2835 used in the PiZero was used in the Nokia 808 PureView as a coprocessor for graphics and the camera: https://en.wikipedia.org/wiki/Nokia_808_PureView

The BCM2763 and BCM2835 are the same silicon in a different package: https://raspberrypi.stackexchange.com/questions/840/why-is-t...

Didn't know that. That makes sense. As a discrete coprocessor to the primary Smartphone SOC for a very high end smartphone, for power management the discrete coprocessor chip can be completely powered down when going into idle mode.

The trick/indicator about the design goal of primary Smartphone SOC usage for the OMAP SOCs and most mobile CPU is the existence of deep sleep, RAM retention modes. Additionally every GPIO pin is configurable for Pull-Up/Pull-Down to prevent current leakage.

I haven't looked extensively but I don't believe the Broadcom SOCs support this mode.

Actually after more extensive review - I think the story is probably that Broadcom attempted to make a smartphone processor from Alpamosaic's Video Coprocessor, but didn't adequately support the low power modes and didn't get any design wins for smart phone.

They then pivoted and found traction in the Over the Top TV space.

https://www.computer.org/publications/tech-news/chasing-pixe...

Some additional reading.

[0] https://www.anandtech.com/show/10716/roku-unveils-streaming-...

Roku Ultra: 900 MHz Broadcom BCM2836 CPU (quad-core)

[1] https://www.anandtech.com/show/4903/roku-2-xs-review-streami...

[2] https://www.reddit.com/r/raspberry_pi/comments/egwo6z/was_th...

[3] https://en.wikipedia.org/wiki/Nokia_N900

[4] https://en.wikipedia.org/wiki/OMAP

There aren't a whole lot of power management features available in the hardware, the SoC just wasn't designed for mobile/battery use. About all you can do is disable USB/ethernet/HDMI if not needed for your use case, or drop the CPU/GPU clocks.

It is relatively low power, in the ballpark of a mobile phone. Running headless the Pi3 consumes 4-5W with an out of the box Ubuntu install, about 9W with the 7" screen, and after shutdown it remains on at about 2W. The iPhone SE takes about 9W while charging and 4W fully charged with the screen on. Numbers aren't exact, read out from a Jackery display and it's been a few months. I think the Pi4 8GB was about 1W more than the Pi3.

Do you know why does it still consume half of the power (2w out of the 4-5w) after shutdown?

The power circuit in the Pi isn't super-efficient.

My Lenovo t460 draws 4-5w while idle with Wi-Fi and lcd goin… 4-5w is a decent draw for headless

For the RPi0W, JG has some hacks: https://www.jeffgeerling.com/blogs/jeff-geerling/raspberry-p...

tl;dr you can drop power consumption to between 80-100 mA at idle if you don't need to use HDMI. And like 75-80 mA if you also disable WiFi/BT completely, as well as the tiny onboard power/activity LED.

But honestly, if you're going to that length and really need good battery life, maybe consider a fast microcontroller ;)

The RPI is horrific for power usage -- I've never understood why they didn't release a version to address this. I get better performance out of all the Friendlyelec stuff....

Certainly one idea was to use the RPi as a battery-powered, pocket-sized, general purpose computer, like a "smartphone". Solutions for this exist but are still awkward, IMO.

Another idea is to use an open source "smartphone" like the PinePhone as a battery-powered, pocket-sized, general purpose computer, like the RPi. (Depite whatever usage the Pine64 folks and "app" contributors envisage.)

The PinePhone boots from SD card, like the RPi. It will run Linux. What remains is further OS support. It will boot NetBSD, which is a start. The RPi battery problem has been solved.

For the avoidance of doubt, "general purpose" means, among other things, "cellular calling" is not a prerequisite to usefuless. Similarly, "pocket-sized" does not imply that the computer is always operated by removing it from a pocket and holding it in the hand; it refers to the form factor, not the usage.

Further, I am not seeking to stimulate discussion of "average users". This is "Hacker News" not "Average User News". The idea has come up a few times on https://forum.osdev.org but I have not seen it discussed on HN.

https://elinux.org/images/d/d4/MischaJonker_ARM11_power_mana...

ARM11 is what the raspberry pi 4 BCM module uses from what I could tell. Looks like your best bet is to set the cpu freq down. I didn't see anything useful in the Broadcom BCM2711 datasheet.

No it isn't? ARM11 are ARMv6 CPUs, Raspberry Pi4 are ARMv8, two generations of difference, and that's just the instruction set. ARM11/ARMv6 says nothing about power management, it's up to the SoC. (ARMv8 does say a few things about power management, but Broadcom/Rasperry Pi4 chose to ignore it)

Ah, well. I did allude to I wasn't certain. That's what I could tell from 5 minutes of sleuthing. Either way the conclusion is the same, you don't have good control to reduce power consumption other than clocking down.

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