Sounds like BCPL is just the thing for you, Ben!
So 1980 - that as the year I discovered Unix and C. I don’t think C has really changed much since then - compilers have gotten better at bleating at you about errors, and producing better code, but that’s more a function of bigger memory, faster cpus, so they can do more. The main change might be K&R style function definitions to ANSI style. longjump is still a thing.
1980 was also the year I first used Primos and wished I hadn’t.
But by 1980 I’d already been using the Apple II (and other micros in a small way) for a couple of years. I missed CP/M early on, but used it in the mid-80’s for a lot of stuff.
The other thing - PL/1 - and PL/M. Bits of CP/M are written in PL/M but I don’t recall ever seeing a compiler for it - but the past few days a video of SPL/M has been published - see
You’re right about modern stuff being too complex though - I have a “bare metal framework” for the Pi 1 and there are bits of it that I could not write, so took the code from elsewhere (the EMMC driver and USB) But using a CPU from the 1980s or making your own shouldn’t be that hard. I’d strongly suggest avoiding the 65816 though.
The BBC Micro does provide an excellent platform for theoretical retro cpu/computer design though - assuming you can write an emulator for your new CPU in either ARM assembler, C or BBC Basic then you can run it on the PiTube co-processor with the Beeb providing the rest in the form of screen, keyboard, filing system, network, etc. That’s my plan for my project when I get some time.
-Gordon