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Comment by bongodongobob | Hacker News Reader

I feel like if your microcontroller needs an OS you should be using an SoC? Genuinely wondering why'd you'd need an OS on a microcontroller.

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The line between "OS" and "not OS" is not binary. It's a blur. For that matter, there's not a clear line between "microcontroller" and "SoC", either.

Does your microcontroller have an external flash? Does it have a file system on that flash? Does that make it need an OS to support the file system?

Does it have enough memory to support allocation to different processes? Does that make it need an OS? And so on.

Right, that's my question. You can use flash and display and whatnot without an OS. When are you using a microcontroller that you'd need the overhead of an OS where an SoC wouldn't be appropriate?

Again, these are not binary. I may decide I need a more feature-full (more "OS-like") task switcher for what I'm trying to do, without going to a full OS (by some definition). I may decide that I need some aspects of SoC in my microcontroller. (Youi can get pretty much any set of features with any core; it's more the number of desktop-like features that makes it a SoC.)

To your specific question: I'm not sure it goes that direction, because a full OS depends on the presence of certain features on the chip. I can think of some examples of it going the other way, though - of an SoC where you don't need or want a full OS.

It's the application that needs an OS, not the computer. It is possible (and isn't unheard of, though decreasingly common) to run software on a more featureful CPU with virtual memory and loads of RAM next door, without an OS, for example.

And it of course depends what one means by "a OS." But, generally, if you are running multiple tasks that might depend on shared resources, you might want an OS---after all, an OS is just something that mediates shared resources among different applications.

You might prefer to use a microcontroller because of power constraints, security (generally easier to mitigate physical attacks and side channels in simpler hardware), or cost and you don't need more resources.

If you're even talking about virtual RAM, you're already in SoC territory. And the concept of an "application" on a microcontroller is foreign to me. I still don't get it.

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