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Raspberry Pi CM0 is an inexpensive compute module with a quad-core ARM Cortex-A53 processor - Liliputing (liliputing.com)
submitted 1 year ago by to c/raspberry_pi@programming.dev
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cross-posted from: https://lemmy.world/post/36384270

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[–] 1 point 1 year ago (2 children)

At that point I'm not sure if there's a point running Linux on such a small device. With 64MB RAM, you won't even be able to run a Python interpreter, let alone any useful services.

You'd probably be better off using a microcontroller. The ESP32-P4 for example has up to 32MB in-package RAM and can deal with extra external SPI RAM.

Without the overhead of running a Linux Kernel, you might even get more performance out of that.

Reasonable points about the CM boards but I don’t see much attraction of the CM0 vs CM4 or CM5. Given that they aren’t after cost minimization, might as well take the extraperformance.

The CM0 is smaller and consumes much less power than a CM4/CM5. It's also way cheaper. They give a range of $18-26, probably depending on how much storage is on there.

In my region the CM5 is €50-€150 and the CM4 is €32-€102. That's a huge difference.

So if you just need a small, low-power compute unit for a cheap handheld device, the CM0 really does make sense.

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  • [–] 1 point 1 year ago (1 child)

    At that point I’m not sure if there’s a point running Linux on such a small device. With 64MB RAM, you won’t even be able to run a Python interpreter, let alone any useful services.

    You can run Python just fine in 64MB (were you thinking 64KB?). I've written substantial multi-threaded Python applications on boards like that. It used to be a lot of memory! But increase it if you want. You can run Micropython pretty comfortably with 64KB by the way. CPython might need more like 1MB, idk.

    The ESP32-P4 for example has up to 32MB in-package RAM and can deal with extra external SPI RAM.

    On https://www.espressif.com/en/products/socs/esp32-p4 it says 768K. 32MB might be possible with SPI ram.

    Without the overhead of running a Linux Kernel, you might even get more performance out of that.

    The OS actually does useful things (multiple processes with memory protection) which is the point of wanting to run it instead of an MCU.

    In my region the CM5 is €50-€150 and the CM4 is €32-€102.

    Yikes, that is pretty expensive, considering that most cheap Android phones have way more compute power AND a phone with a display etc. This is from 2021 and is the type of thing I have in mind:

    https://www.cnx-software.com/2021/03/19/sigmastar-ssd210-tiny-dual-core-arm-cortex-a7-soc-64mb-ram-rgb-display/

    Idk if anything came of it. There was a mention at the time of using it on a Linux board same size as a Seeed Xiao.

    The Pocket Beagle 2 is maybe like a CM4 or rpi 4 and is $29:

    https://www.cnx-software.com/2025/05/22/pocketbeagle-2-rev-a1-board-gets-1-4-ghz-sitara-am6254-quad-core-cortex-a53-cortex-m4f-soc-with-3d-gpu/

    The original Pocket Beagle was priced around the same, from 2017:

    https://www.righto.com/2017/12/hands-on-with-pocketbeagle-tiny-25.html

    Plus of course there is the whole Pi Zero series. Shouldn't these CM's cost less rather than more?

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  • [–] 1 point 1 year ago

    You can run Python just fine in 64MB (were you thinking 64KB?). I've written substantial multi-threaded Python applications on boards like that. It used to be a lot of memory! But increase it if you want. You can run Micropython pretty comfortably with 64KB by the way. CPython might need more like 1MB, idk.

    With a full Linux with a somewhat modern stack? In the 2000s, sure. In 2025? I doubt that.

    On https://www.espressif.com/en/products/socs/esp32-p4 it says 768K. 32MB might be possible with SPI ram.

    Yeah, like I said: the SPI RAM (also called PSRAM) is in-package. It's not a separate package, but integrated inside the ESP32-P4 package. It's only called SPI RAM because internally the ESP32 transparently connects to it via SPI.

    The OS actually does useful things (multiple processes with memory protection) which is the point of wanting to run it instead of an MCU.

    The ESP32 family utilizes FreeRTOS which gives you multiple processes, but sadly no MPU.

    Just depends if you really need memory protection on such a tiny devices. I guess, some use cases need it, but I wouldn't think too many.

    Yikes, that is pretty expensive, considering that most cheap Android phones have way more compute power AND a phone with a display etc.

    Raspberry Pis in all shapes (except maybe the Zero line) are pretty expensive for the hardware.

    But you buy long term support. There's hardly any other SBCs with nearly that level of software and hardware long term support. They sell each of their devices for around 12 years and give software support for at least that time. For low-quantity production, that's amazing.

    At a prior job we designed an optical network bypass tap with a CM3 in it to provide a REST api and a Web UI. It was so simple to build all that and the 12 years of support meant that we didn't have to redesign anything over that time.

    Most other SBC manufacturers are quite spotty with their LTS and their long-term hardware availability.

    Plus of course there is the whole Pi Zero series. Shouldn't these CM's cost less rather than more?

    The cheapest Pi Zero 2W (which is technically identical to the CM0) costs €17.80, which is a bit more than the $18 minimum price from the announcement. The more expensive variant of the CM0 ($26) includes EMMC storage on board which replaces the SD card. €8 isn't exactly much for a large SD card.

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