> I'm reminded that chips like the Intel 8080 and Motorola 6800 were not intended to be general-purpose computers, and were originally designed mostly to be embedded controllers and as building blocks for "real" computers like terminal and disk controllers.

While the proposed use cases were things like that, I'd push back on saying that they weren't "intended to be general-purpose computers". I have the original 8080 manual in front of me, and it's very clear they considered them computers to be applied to problems (the first chapter is literally "The Functions of a Computer"). Oh, and the 8080 manual clearly identifies it as the "Intel 8080 Microcomputer Systems" and the 6800 calls it the "Benchmark Family for Microcomputer Systems"

> I suppose in principle the RPi Pico could self-host its own OS and devel environment. 520 KB of RAM in the old days was plenty to fit an OS and compiler.

With two cheap PSRAM chips and a bit of trickery, you can upgrade that to 32(.5) MB, which is certainly enough to run a small OS.

In principle you can add even more memory with bank switching, but 32 MB is the limit for a flat address space.

uCLinux was a real thing for a good long while, though I think at this point real microprocessors are cheap, simple, and widely available enough that there hasn't been much need.

Which “old days” would those be. Sounds like it would be 50 years ago