Ancestors

Written by Manawyrm | Sarah on 2024-09-01 at 21:22

New blog post:

Executing Linux applications on a Raspberry Pi in less than 3.5s from power-up! 🚀🏎️

(and other power saving tricks)

https://kittenlabs.de/blog/2024/09/01/extreme-pi-boot-optimization/

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Written by Graham Sutherland / Polynomial on 2024-09-01 at 22:49

@manawyrm something worth trying is dropping the 5V supply voltage for the Pi down to 4V. the limited schematics available show the board using PAM2306 and RT8088 buck regulators to derive the 3.3V and VDD_CORE voltage rails. the PAM2306 goes from 60% efficient at 5V up to 85% efficient at 4V in, which is a major increase. the RT8088 gains a couple of percent efficiency by dropping to 4V too.

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Written by Manawyrm | Sarah on 2024-09-02 at 07:32

@gsuberland Holy shit.

I just tried this and yes, you're totally right.

The switching regulator get's vastly more efficient at lower voltages.

I saved 20% total energy by reducing the input voltage down to 3.6V (updated blog post):

https://kittenlabs.de/blog/2024/09/01/extreme-pi-boot-optimization/#reducing-input-voltage

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Written by thomask77 on 2024-09-02 at 07:48

@manawyrm @gsuberland would a zstd compressed kernel save some time?

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Written by Manawyrm | Sarah on 2024-09-02 at 07:50

@thomask77 @gsuberland Yes, saves a bit of time, but the decompression uses lots of energy.

Not the right tradeoff for my application (where total energy is king, not time).

SD cards are fast -- best option would probably be to write a home-grown mini bootloader and read an uncompressed kernel at full 50+ MByte/s.

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Toot

Written by Z̈oé ⛵ on 2024-09-02 at 08:05

@manawyrm @thomask77 @gsuberland I see you’ve benchmarked gzip‘d kernel and intitramfs but zstd is optimized for fast decompression, so it can be a lot faster, and I wonder if it still uses more energy (and which compression setting is optimal)

especially if the video core loads the kernel and that step is slow

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