[rektide]

Original RPi0 supposedly can idle at 0.4W, where-as the 3 (whose cpu this is based on) idles at >1.5W. It's cool to have this great small package, but this is a very different offering than the first RPi0W.

It's felt really weird seeing so little progress in available low power ARM over the years. Atmel/Microships SAMA5D3 / SAMA5D2 with it's 600 MHz Cortex A5 (2009) still seems like- half a decade latter- one of a rare few genuinely low power Linux running SoC available for purchase/use. I'm forgetting what's available in the Cortex A7 line, which is a little higher power but which still has some very low power chips available for it, & at significantly higher performance ranges. A7 has a lot of chips you can't buy, only available in some tablets & or hard to get wearable chips, but I think there are some good offerings about too. ST has the ~$20 STM32MP1, to name one.

Yet I just see so much non-materialization, non-availability. It feels like the rule. 2015's Cortex A35, 2016's Cortex A32, 2019's Cortex-A34... none of these chips seem to have really materialized in any genuinely available form. There are some off-brand tablets with A35 chips but generally that's about it. The low power segment has been rather ignored.

[zxcvgm]

The processors on the Pis aren't really optimized for low power, and they aren't strictly ARM. These Broadcom chips have a VideoCore that starts up first, which then brings up the ARM cores (geerling goes into greater detail here [0]). I don't think there was any kind of work done to properly suspend both cores for sleep modes.

If you're looking for low power ARMs, maybe other boards may fit the bill better.

[0] https://www.youtube.com/watch?v=DHwL1_afSn8

[geerlingguy]

The Pi 3 model A/B have a lot more electronics—check my video and blog post about the Pi for more on power efficiency—the Zero 2 W can run at 0.6W (100 mA) vs the Zero W at 0.4W (80 mA).

Both idle a little higher if you're actively using HDMI and WiFi.

[zokier]

i.mx8 Nano supposedly can idle at <0.2W, with max power somewhere around 2W. They have also announced ULP version if i.mx but that seems somewhat vaporware at this point.

As for the relative unpopularity of Cortex A3x series, I suspect that might partly because Cortex M series has been creeping into similar performance territory, like for example the i.mx rt mcu on Teensy 4.x, which has Cortex M7 running at 600 MHz.

[seabird]

"Low power" and "something that runs an OS as heavy as Linux" are two conflicting features.