Extremely Brief History of PDP Computers

A timeline of Digital Equipment Corporation’s PDP machines compares minimum-configuration prices, adjusted for inflation, with memory-cycle time as a rough measure of speed. The PDP-1 began as an experiment in whether customers would use general-purpose computers for industrial control, rather than people or dedicated logic systems. DEC then developed two related but incompatible paths: the PDP-4, later upgraded into the PDP-7 and PDP-9, emphasized lower cost and improved performance; the smaller PDP-5, which became the PDP-8, was designed to make control applications cheaper still. The PDP-6 was a distinct, larger system built for time-sharing, memory protection, and extensive directly addressable memory, making it especially capable of running large Lisp programs. The PDP-10 followed it, while the PDP-11 sought to unify DEC’s product lines; the later VAX eventually took over much of the PDP-10’s role.

The machines’ different capabilities and costs helped create distinct computing cultures. The PDP-7 and PDP-11’s limited resources shaped Unix, C, and tools such as vi, make, awk, and Usenet around compact, efficient systems and time-sharing. By contrast, the PDP-10’s abundant memory and processing capacity supported resource-intensive projects including Emacs, Lisp dialects, Scheme, TeX, Zork, and Microsoft BASIC. This divide reflected institutional budgets as much as technical taste: Bell Labs favored doing more with less, while MIT benefited from substantial DARPA funding. The history links hardware constraints and organizational circumstances to the forms of software and hacker culture that emerged.