Working at Control Data, founded by Bill Norris 1956, made successful through the work of Seymour Cray (a "real programmer"). When I worked there, it was nummber 3 of the computer companies, later in 1999 it was bought by British Telecom.
These are not racks, this is all just 1 computer, a mainframe. It spans from the left to the right, with more doors and assemblies of circuit boards on the sides hidden out of view. There are also circuit board assemblies inside the massive doors. This very compact construction was necessary in order to shorten the time for the signal to reach other parts of the computer system. For a picture of the sandwich curcuit boards follow the link.
Control Data History Page