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.
Comments
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