I think it's important to remember our cousins at Data General and their Nova and Eclipse series too. DEC and DG had the best groups of computer scientists the

I think it's important to remember our cousins at Data General and their Nova and Eclipse series too. DEC and DG had the best groups of computer scientists the world has ever seen in one place and I don't think PDP11 or VAX11 would have come out so good without such stiff competition from DG Nova and Eclipse. (Youngling computer scientists, mandatory reading "The Soul of a New Machine".) Also, modern people should realize that electrical interfaces on old 1960s-70s mainframes were almost always locked down by license agreements (as in "touch the backplane in an 'unapproved way' and your institution could be charged thousands of dollars in 'service' fees.”) With mainframes locked down and costing so much money to operate, one couldn't exactly do anything particularly exciting with them beyond mundane information management tasks. ALL of the real action, including creation of UNIX, C-Language, controlling the public phone system switches, aerospace platforms, laboratory c&c, numerical control, industrial process automation, etc. was happening on "mini" computers that were relatively cheap, could be electrically interfaced to almost anything, impacted less users during system-level operations and (usually) were pretty easy to fix. But IBM, CDC, Burroughs, Sperry, etc. had no real financial interest in creating "mini" computers, so employee spin-outs like DEC and, in turn, Data General happened. In DEC's case, they grew so successful they even tried to produce a couple of their own "sub-mainframes" like the PDP-6/10/20 (aka DECsystem10/20 series), but their core competency was hardware-level computer science until the VAX. The VAX (and DG Eclipse) came in as the 1970s were ending, because IBM and other mainframe manufacturers were flying “too high” on sales that supported "information technology" needs, but DEC and DG were seeing erosion from VLSI-based microprocessors sold by Motorola, RCA and Mostek. DEC responded with LSI-11 but also divestiture to a new class of computers, decentralized systems that would ultimately be called "departmental computers" that could network with each other and thereby eliminate (or at least supplement) the need for expensive big iron mainframes. With newer and better PDPs in tow, DEC began to tear into IBM's mainframe market with cheaper and cheaper VAXen. (Unfortunately, a kid named Bill Gates was dedicating himself to enable microprocessor-based computers to do the same to the VAX that VAX had done to mainframes, ironically using an old PDP-10 at Harvard to prototype his code…a decade or so later leading to DEC being acquired by Compaq and then destroyed by the mismanagement of Carly Fiorina.)