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For those that have tried many single-board computers, which one has the lowest power consumption while still being able to run Linux with WiFi and audio? It’s fine with me if it’s using an old 32-bit ARM architecture, even lacking soft floating point. I’m interested in power consumption both under load and at idle (but not sleeping, i.e. ready to act on user or network input), but I think the latter is more important. Thanks!

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      Most audio applications really need floating point performance. Not, mind you, modern floating point performance, but nevertheless, more than is usually available in soft-fp systems.

      Can we ask what your intended use is?

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        Soft fp is also less power-efficient by definition, in addition to old soft-fp-only chips being less efficient due to, uh, being old – made on an older process.

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        The intended use is a mobile personal computer (what we used to call a PDA) for blind people. So no screen, but a physical keyboard (probably a braille one) and audio output, including text-to-speech. It was possible to do good text-to-speech on 90s PCs, so I’m not worried about having enough processing power for that. Being able to play lossily compressed audio formats like MP3 is also important. Encoding audio in a low-bit-rate format such as Opus would also be needed for some applications, such as voice calls or recording voice memos.

        Edit: Being able to run one of the big three web browser engines, or a GUI of any kind, is specifically not a goal. I’m curious about how good battery life can be if we don’t start with the assumption that the device has to be compatible with the mainstream web.

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          OK, so your use case is:

          • Stereo audio out, microphone in (mono or stereo)
          • 2+ USB2 ports for braille display and keyboard
          • wifi for networking
          • long battery life
          • no need for video display or touchscreen digitizer
          • nice if it had a haptic buzzer, perhaps

          This sounds like a job for one of the power-optimized ARM SOCs from RockChip or NXP. You can get all of that on a test board for cheap to ridiculously cheap, usually with 256MB - 1 GB RAM and some MMC storage, everything else on breakout pins. They all run Linux, though often with silly bootloaders. I can’t specify an exact one because everybody is out of everything right now…

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      I’m not really recommending this for anything serious, but it might be the ESP32: https://hackaday.com/2021/07/21/its-linux-but-on-an-esp32/

      Due to the external hardware this one is probably not the cheapest, but very impressive nonetheless: https://hackaday.com/2012/03/28/building-the-worst-linux-pc-ever/ (although it does not meet your hardware requirements)

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      Leave the display DPMS off and you’ll find pinephone to have a fair power consumption as well. Might not be the cheapest BoM depending on where you are in the funding/development/prototype stages, but having most of the bring-up done and the other niceties e.g. IMU to detect being dropped and alerting to location and so on. If I recall the schematics correctly you do lack microphone array for doing beam forming in noisy environments, but that can perhaps be fixed …