1970 DEC PDP-11

PDP-11 was a series of 16-bit minicomputers manufactured by Digital Equipment Corp. in the 1970s and 1980s. It pioneered the interconnection of all system elements—processor, RAM, and peripherals—to a single, bidirectional, asynchronous communication bus. This device, called Unibus, allowed devices to send, receive, or exchange data without the need for an intermediate memory pass. The PDP-11 series was one of the best-selling minicomputer series of its time and one of the first to run the Unix OS, developed at Bell Labs.

The series has evolved with the advancement of technology, going from a CPU consisting of TTL MSI integrated circuits to microprocessors such as the LSI-11. The latest versions, from PDP-11/75 onwards, incorporated the J-11, with duplicate registers, three stacks (User, Core and Supervisor), virtual memory (22 bits), cache and separate memory spaces for instructions and data. It was a very ambitious chip for the time, but it never quite lived up to expectations, due to design issues and discussions between DEC and Harris Semiconductor, the chip maker.

During the Cold War, the architecture of the PDP-11 series was cloned in the USSR without authorization from the manufacturer. In this way, programs developed for the series could run smoothly on the Soviet clones.

A modern PDP-11 replica using Raspberry PI is available at PDP-11

Filed under: 70s Computers,Honorable Mentions - @ January 31, 2022 10:49 AM