page_title: History of Digital Equipment Corporation
section_title: PDP-1 family
hierarchical_section_title: History of Digital Equipment Corporation / PDP-1 family
caption_attribution_description: English: Steve Russell and the Computer History Museum's PDP-1. Français&#160;: Steve Russell et le PDP-1 du Musée de l'histoire de l'ordinateur.
context_page_description: Digital Equipment Corporation, was a major American company in the computer industry. Founded in 1957 with $70,000 of venture capital, it became "the nation's second-largest computer company, after IBM." Its initial major impact was in minicomputers, but its later-introduced VAX and Alpha systems are still notable.
  DEC was acquired in June 1998 by Compaq, in what was at that time the largest merger in the history of the computer industry. Not long thereafter, Hewlett-Packard bought Compaq,
  "creating a technology company second in revenue only to IBM."
  Aside from the company's extensive hardware and software accomplishments, it was also noteworthy for its use of Matrix management
context_section_description: With the company established and a successful product on the market, DEC turned its attention to the computer market once again as part of its planned "Phase II". In August 1959, Ben Gurley started design of the company's first computer, the PDP-1. In keeping with Doriot's instructions, the name was an initialism for "Programmable Data Processor", leaving off the term "computer". As Gurley put it, "We aren't building computers, we're building 'Programmable Data Processors'." The prototype was first shown publicly at the Joint Computer Conference in Boston in December 1959. The first PDP-1 was delivered to Bolt, Beranek and Newman in November 1960, and formally accepted the next April. The PDP-1 sold in basic form for $120,000 (equivalent to $7,778,065 in 2019). By the time production ended in 1969, 53 PDP-1s had been delivered.
  The PDP-1 was supplied standard with 4096 words of core memory, 18-bits per word, and ran at a basic speed of 100,000 operations per second. It was constructed using many System Building Blocks that were packaged into several 19-inch racks. The racks were themselves packaged into a single large mainframe case, with a hexagonal control panel containing switches and lights mounted to lie at table-top height at one end of the mainframe. Above the control panel was the system's standard input/output solution, a punched tape reader and writer. Most systems were purchased with two peripherals, the Type 30 vector graphics display, and a Soroban Engineering modified IBM Model B Electric typewriter that was used as a printer. The Soroban system was notoriously unreliable, and often replaced with a modified Friden Flexowriter, which also contained its own punched tape system. A variety of more-expensive add-ons followed, including magnetic tape systems, punched card readers and punches, and faster punched tape and printer systems.
  When DEC introduced the PDP-1, they also mentioned larger machines at 24, 30 and 36 bits, based on the same design. During construction of the prototype PDP-1, some design work was carried out on a 24-bit PDP-2, and the 36-bit PDP-3. Although the PDP-2 never proceeded beyond the initial design, the PDP-3 found some interest and was designed in full. Only one PDP-3 appears to have been built, in 1960, by the CIA's Scientific Engineering Institute (SEI) in Waltham, Massachusetts. According to the limited information available, they used it to process radar cross section data for the Lockheed A-12 reconnaissance aircraft. Gordon Bell remembered that it was being used in Oregon some time later, but could not recall who was using it.
  In November 1962 DEC introduced the $65,000 PDP-4. The PDP-4 was similar to the PDP-1 and used a similar instruction set, but used slower memory and different packaging to lower the price. Like the PDP-1, about 54 PDP-4's were eventually sold, most to a customer base similar to the original PDP-1.
  In 1964 DEC introduced its new Flip Chip module design, and used it to re-implement the PDP-4 as the PDP-7. The PDP-7 was introduced in December 1964, and about 120 were eventually produced. An upgrade to the Flip Chip led to the R series, which in turn led to the PDP-7A in 1965. The PDP-7 is most famous as the original machine for the Unix operating system, and until the Interdata 8/32 Unix only ran on DEC systems.
  A more dramatic upgrade to the PDP-1 series was introduced in August 1966, the PDP-9. The PDP-9 was instruction-compatible with the PDP-4 and −7, but ran about twice as fast as the −7 and was intended to be used in larger deployments. At only $19,900 in 1968, the PDP-9 was a big seller, eventually selling 445 machines, more than all of the earlier models combined.
  Even while the PDP-9 was being introduced, its replacement was being designed, and was introduced as 1969's PDP-15, which re-implemented the PDP-9 using integrated circuits in place of modules. Much faster than the PDP-9 even in basic form, the PDP-15 also included a floating point unit and a separate input/output processor for further performance gains. Over 400 PDP-15's were ordered in the
caption: A PDP-1 system, with Steve Russell, developer of Spacewar! at the console. This is a canonical example of the PDP-1, with the console typewriter on the left, CPU and main control panel in the center, the Type 30 display on the right.
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