I know it's taboo to talk about the TRS-80 and its descendants in C64 company, but did anyone else have a CoCo3? Loved that thing to death.
Neatest feature about it was that it had the OS in ROM, but dumped it to RAM. So you could just use the OS designated RAM for your own flavor. Like getting the third-party ADOS and going through the commented code to tweak your OS to your liking, changing disk read times, etc.
It was a lot of fun.
I grew up on a CoCo3; loved that thing as well :) OS-9 Level II was where I first learned a Unix-like OS (on a tiny 6809 machine!) OS-9 Level II was truly a remarkable achievement for such a tiny machine: multi-tasking, windowing, and more. Dungeons of Daggorath was also an epic game. Basic09 was an interesting Basic-dialect that provided more structural programing to the normal sprawling Basic program. And of course who could forget Rainbow Magazine.
I was pro-Apple and anti-Tandy back then, so I looked down on the CoCo and didn't realize how cool a computer it was until later. Now that I'm older and wiser (?) I realize how silly technology partisanship is. Each device and technology should be evaluated on its own merits and not by which camp it comes from.
Old habits are hard to break! I took a fun loving shot at TRS-80s on the cOS Test/Demo disk. There is a goofy Windows 9 "release" on there where I labeled the trash can... wait for it... "TRS-80". I just saw some old CoCos at a vintage computer show. Actually really cool what people were doing with them!
You could do the same with the C64 (probably quite a few other 80's home machines). The ROM's were bank-switched in, and if you want to you can copy the ROM into RAM and switch out the ROM banks. Quite a few extensions made use of that.
edit for typo