PDP and VAX

Digital Equipment Corporation (abbreviated to DEC), was founded in 1957 by two engineers, Kenneth Olsen and Harlan Anderson, graduates of Massachusetts Institute of Technology, and was one of the oldest and most known companies of the world computer industry.

Before founding, Olsen worked for Lincoln Laboratory at the institute mentioned above, which was supported by the Department of Defense (USA), and participated in development of one of world's first transistor-based computers, TX-2. The company was producing and selling backplane modules for computers initially, but in 1960 it offered the first computer of its own, 18-bit PDP-1 (Programmable Data Processor - 1), able of completing about 100 thousand operations per second. By the way, that machine was used to run the first computer game in history, Spacewar of Steven Russell. 12-bit PDP-8, which was introduced in 1964, deserved to be called the first "minicomputer" (with the size of a small wardrobe) manufactured in mass quantities. Also, the price was attractive: about 18,000 USD (in 1965) for a standard configuration. Because of an excellent price/performance ratio, PDP-8 was able to compete with those famous IBM mainframe systems quite successfully. There were about 1450 machines produced by 1968 (not counting numerous modifications following). 36-bit PDP-10 was ready in the same 1968, based upon the design of an experimental PDP-6, and targeted for data processing centers, research laboratories, and military needs. Different versions of PDP-10 were manufactured until 1983. They kept working on the 36-bit architecture improvement within the Unicorn project under supervision of Leonard Hughes and David Rogers, but the project was closed in June 1975, and all its resources were transferred to support another, 32-bit, architecture.

16-bit PDP-11, was launched in production in the beginning of 1970's. It was the first DEC's computer to use 8-bit bytes, and a direct successor to the PDP-8 product line. Due to a simple and fortunate Unibus-based architecture (or a modified one, based upon Q-bus), a considerably effective instruction set, and low manufacturing costs, which was also very important, the PDP-11 product line turned a success. Of course, they started cloning PDP-11 all over the world very soon, including even those "countries of people’s democracy". They released CM-4 (USSR, Bulgaria, Hungary), CM-1420 (USSR, Bulgaria, German Democratic Republic), CM-1600 (USSR), IZOT-1016 (Bulgaria), DVK (USSR). There were many operating systems developed for PDP-11: DEC offered P/OS, RSX-11, RT-11, RSTS/E, also several derivatives of DOS, and finally, the first release of UNIX OS was completed in Bell Laboratories on PDP-7 and PDP-11 machines in 1971, in assembler. PDP-11 left the market during 1980's because of one, but inevitable reason: lack of address space. This is when a new, 32-bit though still CISC, architecture was promoted to the market.

And that architecture was VAX (Virtual Address eXtension). It was approved officially during a VAX Architecture Committee session in April 1975. They have been working on this architecture for several months within the Star project supervised by Gordon Bell, in parallel with the Unicorn project mentioned above. Once both projects had been completed, they decided to cancel any further development of 36-bit systems, and to concentrate resources available to support 32-bit VAXen (plural of VAX). In fact, the Star project was to prove the necessity of increasing general registers' width of PDP-11 to 32 bits, their number from 8 to 16, and a significant redesign of the instruction set. The first VAX machine was announced in October of 1977, model 11/780. A few months later, in February of 1978, they released a new operating system for VAXen, VMS (Virtual Memory System) v1.0. It was a multi-user and multi-tasking OS supporting up to 64MB of main memory, had networking functions implemented (DECnet), also an adaptive task scheduler, an extended process management, and many other innovations never seen before. Renamed to VAX/VMS, v2.0 was presented in April of 1980, carrying numerous improvements. Also, the classical UNIX was ported to VAX pretty soon. VAXen were manufactured and sold really successfully during 1980s, and were shipped in limited quantities according to special contracts even close to the end of the century. The whole product line included several dozens of models, ranging from compact workstations to 6-processor mainframe-class servers. Even nowadays, thousands of VAXen keep working in the Department of Defense and the NSA (National Security Agency) of the United States, as well as in numerous commercial organizations. Nevertheless, the epoch of VAXen was 1980s, and in 1990s DEC bet on a new architecture.