I'm working on a project to write a small OS based loosely on the functionality of CP/M. I want to better understand a few things about the early home computing market, as well as to understand operating systems concepts. I'm using a Cortex M0+, which has, among other things, 8K of RAM. From this perspective, the Cortex M0+ can't even run CP/M, which required a minimum 16K of RAM. However, it is also much faster, at 48MHz, plus a bunch of modern enhancements. So here's the question: can this microcontroller be used in a meaningful way to explore these concepts, or is it so different from what came before that the changes I'll have to make to my OS compared to early ones would be too significant?
Second, was there an early OS that ran on something with 8K of RAM that still had a reasonable user interface? Or perhaps a better question, why did CP/M require 16K of RAM? What did it use all of it for?
Ostensibly I can just buy a bigger microcontroller, but part of what I'm trying to do is better understand the need for efficiency. Today, I could just write the OS for an old laptop or something and have access to GB of memory, but that's not the point!