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The $8 Linux Computer

thelittleengineerthatcould.blogspot.com

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Re: The $8 Linux Computer

#131

Post by monocasa »

alexisread wrote: post #20
mmuless22 wrote: post #13

what is the memory management unit supposed to do on embedded computers? I'd rather like one for 5$ without mmu.

This chip has 4 cores, and I believe they all share the same memory bus ie. Each core can access the 64GB ram directly. There is also 768K sram for low power use. Only the RV64 large core has an mmu, the two RV32 cores don't. I think the chip's main use could be robotics- the lowest power core for networking, npu for image processing, the mid core for simple tasks and the large core for Linux and complex tasks eg. Na…

> This chip has 4 cores

3 cores

> For your use then, you could just use the lowest power microcontroller with 64GB ram. You can't get that ability anywhere else.

I don't think the LP core has access to PSRAM. So most of the networking would run on the mid core, and the LP core just makes decisions to wake up a bigger core based on the events it sees.

Re: The $8 Linux Computer

#132

Post by monocasa »

alexisread wrote: post #102
aswanson wrote: post #61

Earlier quoted context omitted.

Any experience with this board? Toolchain, etc?

Not yet- I have a maix M1s dock full package on order, so hope to try it shortly. Sipeed supply a connector to be able to flash their board easily, and they seem to have an IDE for various use cases. I'm hoping the MCU in the chip is the same as the BL602 chip- the 602 has a fully opensource firmware for the radio and cpu, can run zig and lora: https://lupyuen.github.io/ For me, I'm looking forward to using a riscV M…

> I'm hoping the MCU in the chip is the same as the BL602 chip

It's not, but it's similar. The BL602 has a SiFive E24, the cores in the BL602 are all T-Head cores (the mid core is a T-Head e907).

Re: The $8 Linux Computer

#133

Post by monocasa »

guerrilla wrote: post #55
jesprenj wrote: post #52

Earlier quoted context omitted.

https://www.kernel.org/doc/Documentation/nommu-mmap.txt

Ok fair enough, Linux can't run normally without an MMU. It kind of defeats the purpose of using a UNIX, but yes, you get all the Linux drivers and the UNIX API for free.

You still have processes and mutual protection between them and the kernel with no-MMU, they just get less options about where they can mmap(2) and you have to vfork(2) instead of fork(2).

Otherwise it feels like a pretty standard Linux.

Re: The $8 Linux Computer

#134

Post by monocasa »

AtlasBarfed wrote: post #121
imhoguy wrote: post #101

We could have pretty decent $8 Linux machines, with USB, screen, touch, audio, MBs or even GBs RAM, if there would be some standard way to sideload fresh GNU/Linux onto billions of retired Android devices.

I thought you could root them and install Linux? But yeah, we need to recycle these phones by making them home servers, etc.

Depends on the phone. It's been getting more difficult.

Re: The $8 Linux Computer

#135

Post by TJSomething »

turbobooster wrote: post #36

Why would you use this instead if some rpi version?

Currently, RPis are quite difficult to obtain and have been since 2020. I was just looking at a project design that required 2 RPi Zero 2 Ws and I'm currently considering alternatives. Unfortunately, the software stack is Java, so I don't think this will work.

Re: The $8 Linux Computer

#136

Post by HPsquared »

imhoguy wrote: post #101

We could have pretty decent $8 Linux machines, with USB, screen, touch, audio, MBs or even GBs RAM, if there would be some standard way to sideload fresh GNU/Linux onto billions of retired Android devices.

The Termux app provides a pretty good fraction of the useful Linux stuff. It's basically a userspace chroot environment. You can run a lot of Linux distributions this way, though some of the features don't work. Can even have a desktop environment and run things like desktop Chromium. Or things like FTP servers, etc etc.

Basically you get most of the useful functionality from installing Linux, without needing root.

Re: The $8 Linux Computer

#137

Post by guerrilla »

monocasa wrote: post #133
guerrilla wrote: post #55

Earlier quoted context omitted.

Ok fair enough, Linux can't run normally without an MMU. It kind of defeats the purpose of using a UNIX, but yes, you get all the Linux drivers and the UNIX API for free.

You still have processes and mutual protection between them and the kernel with no-MMU, they just get less options about where they can mmap(2) and you have to vfork(2) instead of fork(2). Otherwise it feels like a pretty standard Linux.

How is that possible without page fault exceptions or equivalent?

Re: The $8 Linux Computer

#138

Post by monocasa »

jazzyjackson wrote: post #128
monocasa wrote: post #122

Earlier quoted context omitted.

Linux has just as much native support for such things as Windows does, if not more.

I mean maybe you're right at this point but it's not like the reputation is undeserved

I mean, we're going on close to 30 years or so that Linux has had parity with Windows for the kind of driver we're talking about: loadable kernel driver for a weird accelerator core that takes firmware but doesn't really fit into a driver model otherwise.

On Linux this is a module that exposes a character device with one off ioctls.

On Windows this a kernel mode driver that exposes a Device object with one off DeviceIoControls.

I really don't think the reputation is deserved in this case, both kernels added equivalent support for this workflow back in the 90s.

Re: The $8 Linux Computer

#139

Post by monocasa »

guerrilla wrote: post #137
monocasa wrote: post #133

Earlier quoted context omitted.

You still have processes and mutual protection between them and the kernel with no-MMU, they just get less options about where they can mmap(2) and you have to vfork(2) instead of fork(2). Otherwise it feels like a pretty standard Linux.

How is that possible without page fault exceptions or equivalent?

The MPU gives you an equivalent of page fault exceptions. You can't remap virtual addresses to physical, but you can change their permissions, trap into the kernel when those permissions are violated, and restart execution of processes after the trap (to deliver signals or what have you).

Re: The $8 Linux Computer

#140

Post by imhoguy »

HPsquared wrote: post #136
imhoguy wrote: post #101

We could have pretty decent $8 Linux machines, with USB, screen, touch, audio, MBs or even GBs RAM, if there would be some standard way to sideload fresh GNU/Linux onto billions of retired Android devices.

The Termux app provides a pretty good fraction of the useful Linux stuff. It's basically a userspace chroot environment. You can run a lot of Linux distributions this way, though some of the features don't work. Can even have a desktop environment and run things like desktop Chromium. Or things like FTP servers, etc etc. Basically you get most of the useful functionality from installing Linux, without needing root.

I use Termux as my daily driver, but I never thought it can run desktop stuff. Still HW (Samsung) is locked down a bit as it doesn't allow autostart after power failure or can't power up without battery.
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