I was always wondering, how big and complex projects, like this one are made in those days. Today it is very much different, you can simulate almost everything, including hardware in hardware. In those days, it requires much more knowledge, time and devotion to bring out something like this. I remember, long time ago ( in galaxy, far, far away, off course ) i was trying to make programable digital timer for photography, made entirely in TTL logic, ok, this one came to documentation phase only, no prototype has been made, but it was hundreds, and hundreds of hours, shitload of printed documentation, and all done on paper and all simulations are done in head. Today, i would not even think of TTL logic, and not even try to assemble anything before simulation. Probably not even put anything on paper at all, it will all be in digital form.