I had a course like that in my CS programme, and even though we really, really didn't go deep, we wired our own super simple 8-bit processor, and wrote the micr

I had a course like that in my CS programme, and even though we really, really didn't go deep, we wired our own super simple 8-bit processor, and wrote the microcode, and then wrote a program in assembly to do something. Stepping through the fetch-execute cycle one cycle at a time, watching your CPU do its little thing, and then realizing that that is exactly what actual CPUs do, they're just doing it billions of times per second, that was amazingly eye-opening.