I’ve always wanted to do this. I helped my housemates implement a CPU with custom ISA in college (this was before FPGAs, so there were a lot of chips in that CPU) but that’s as close as I’ve gotten.
I kind of feel like you can do something like this in college, or after you retire, but nowhere in between. :)
Why not? I made my first Phone OS (RTOS) on 8051 and 256KB ROM in college 20 years ago. Then I worked on several projects and my skills improved. Then I designed a processor architecture, made C-like programming language, created a compiler, an IDE, created a mobile OS and want to build a hardware chip in my startup https://animationcpu.com/
That’s awesome! To be clear, I’ve been able to pick (or create) some fantastic “day jobs” where I got to do lots of things I wanted to do. For some reason it’s harder for me to focus on a big long-term “outside interest” project like this. But you’re exactly right...why the heck not?
I kind of feel like you can do something like this in college, or after you retire, but nowhere in between. :)