I'm reading the excellent "The soul of a new machine" by Tracy Kidder right now. Your post has helped visualize the types of computers mentioned in the book.
That's a great book. Keep in mind that the computer in "The soul of a new machine" (Data General Eclipse MV/8000) was a minicomputer, not a mainframe, and in 1980, not 1964. So there are a lot of differences as well as similarities. (I'm not trying to be pedantic, but just want to make sure you don't get the wrong impression of the Eclipse.)
Technically it was a 32-bit so-called "supermini" analogous to the VAX rather than a smaller 16-bit machine like most classic minicomputers (PDP-11, DG Nova/Eclipse).
Wonderful book. There's a snippet on conflicts between engineers and how engineers approach them - often not in the best way - that I've referenced so many times in my career.
Great book. I relentlessly and boringly quote the commandment from the CEO in that book that there was to be "no mode switch".
I have found this to be a great rule of thumb in software too. Engineers often first instinct is to add "advanced mode", "legacy mode" or whatever. Often with no idea how much trouble having two modes of behaviour will cause downstream in training, understanding, compatibility etc.