Digital Equipment Corporation (DEC)

Using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president until he was forced to resign in 1992, after the company had gone into precipitous decline. The company produced many different product lines over its history. It is best known for the work in the minicomputer market starting in the early 1960s. The company produced a series of machines known as the PDP line, with the PDP-8 and PDP-11 being among the most successful minis in history. Their success was only surpassed by another DEC product, the late-1970s VAX "supermini" systems that were designed to replace the PDP-11. Although a number of competitors had successfully competed with Digital through the 1970s, the VAX cemented the company's place as a leading vendor in the computer space. As microcomputers improved in the late 1980s, especially with the introduction of RISC-based workstation machines, the performance niche of the minicomputer was rapidly eroded. By the early 1990s, the company was in turmoil as their mini sales collapsed and their attempts to address this by entering the high-end market with machines like the VAX 9000 were market failures. After several attempts to enter the workstation and file server market, the DEC Alpha product line began to make successful inroads in the mid-1990s, but was too late to save the company. DEC was acquired in June 1998 by Compaq in what was at that time the largest merger in the history of the computer industry. During the purchase, some parts of DEC were sold to other companies; the compiler business and the Hudson Fab were sold to Intel. At the time, Compaq was focused on the enterprise market and had recently purchased several other large vendors. DEC was a major player overseas where Compaq had less presence. However, Compaq had little idea what to do with its acquisitions, and soon found itself in financial difficulty of its own. Compaq was eventually bought by Hewlett-Packard in May 2002. 

Origins (1944–1958)

Ken Olsen and Harlan Anderson were two engineers who had been working at MIT Lincoln Laboratory on the lab's various computer projects. The Lab is best known for their work on what would today be known as "interactivity", and their machines were among the first where operators had direct control over programs running in real-time. These had started in 1944 with the famed Whirlwind, which was originally developed to make a flight simulator for the US Navy, although this was never completed] Instead, this effort evolved into the SAGE system for the US Air Force, which used large screens and light guns to allow operators to interact with radar data stored in the computer. When the Air Force project wound down, the Lab turned their attention to an effort to build a version of the Whirlwind using transistors in place of vacuum tubes. In order to test their new circuitry, they first built a small 18-bit machine known as TX-0, which first ran in 1956. When the TX-0 successfully proved the basic concepts, attention turned to a much larger system, the 36-bit TX-2 with a then-enormous 64 kWords of core memory. Core was so expensive that parts of TX-0's memory were stripped for the TX-2, and what remained of the TX-0 was then given to MIT on permanent loan.

At MIT, Ken Olsen and Harlan Anderson noticed something odd: students would line up for hours to get a turn to use the stripped-down TX-0, while largely ignoring a faster IBM machine that was also available. The two decided that the draw of interactive computing was so strong that they felt there was a market for a small machine dedicated to this role, essentially a commercialized TX-0. They could sell this to users where the graphical output or real-time operation would be more important than outright performance. Additionally, as the machine would cost much less than the larger systems then available, it would also be able to serve users that needed a lower-cost solution dedicated to a specific task, where a larger 36-bit machine would not be needed.

In 1957, when the pair and Ken's brother Stan sought capital, they found that the American business community was hostile to investing in computer companies. Many smaller computer companies had come and gone in the 1950s, wiped out when new technical developments rendered their platforms obsolete, and even large companies like RCA and General Electric were failing to make a profit in the market. The only serious expression of interest came from Georges Doriot and his American Research and Development Corporation (AR&D). Worried that a new computer company would find it difficult to arrange further financing, Doriot suggested the fledgling company change its business plan to focus less on computers, and even change their name from "Digital Computer Corporation" The pair returned with an updated business plan that outlined two phases for the company's development. They would start by selling computer modules as stand-alone devices that could be purchased separately and wired together to produce a number of different digital systems for lab use. Then, if these "digital modules" were able to build a self-sustaining business, the company would be free to use them to develop a complete computer in its Phase II. The newly christened "Digital Equipment Corporation" received $70,000 from AR&D for a 70% share of the company, AR&D's SVP Dorothy Rowe joined as a Director and also served as Treasurer, and the company began operations in a Civil War-era textile mill in Maynard, Massachusetts, where plenty of inexpensive manufacturing space was available.

1957 

August:
Ken Olsen and Harlan Anderson found Digital Equipment Corporation and set up shop in an old woolen mill in Maynard, Massachusetts.Digital opened for business with three employees and 8,500 square feet of production space in this converted 19th-century woolen mill.

The company's first product is laboratory modules.
Laboratory modules were intended to sit on an engineer's workbench or be mounted in a scientist's equipment rack. To simplify the construction of logic systems, the modules were connected by simple cords with banana plugs.

1958

In early 1958, DEC shipped its first products, the "Digital Laboratory Module" line. The Modules consisted of a number of individual electronic components and germanium transistors mounted to a circuit board, the actual circuits being based on those from the TX-2.
The Laboratory Modules were packaged in an extruded aluminum housing, intended to sit on an engineer's workbench, although a rack-mount bay was sold that held nine laboratory modules. They were then connected together using banana plug patch cords inserted at the front of the modules. Three versions were offered, running at 5 MHz (1957), 500 kHz (1959), or 10 MHz (1960).
The Modules proved to be in high demand by other computer companies, who used them to build equipment to test their own systems. Despite the recession of the late 1950s, the company sold $94,000 worth of these modules during 1958 alone (equivalent to $1,049,000 in 2025), turning a profit at the end of its first year.
The original Laboratory Modules were soon supplemented with the "Digital System Module" line, which were identical internally but packaged differently. The Systems Modules were designed with all of the connections at the back of the module using 22-pin Amphenol connectors, and were attached to each other by plugging them into a backplane that could be mounted in a 19-inch rack. The backplanes allowed 25 modules in a single 5-1/4 inch section of rack, and allowed the high densities needed to build a computer.
The original laboratory and system module lines were offered in 500 kilocycle, 5 megacycle and 10 megacycle versions.
In all cases, the supply voltages were -15 and +10 volts, with logic levels of -3 volts (passive pull-down) and 0 volts (active pull-up).
DEC used the System Modules to build their "Memory Test" machine for testing core memory systems, selling about 50 of these pre-packaged units over the next eight years. The PDP-1 and LINC computers were also built using System Modules.
Modules were part of DEC's product line into the 1970s, although they went through several evolutions during this time as technology changed. The same circuits were then packaged as the first "R" (red) series "Flip-Chip" modules. Later, other Flip-Chip module series provided additional speed, much higher logic density, and industrial I/O capabilities. DEC published extensive data about the modules in free catalogs that became very popular.

February:
Digital's second product, Systems Modules, goes on the market.
Systems Modules or "DIGITAL Building Blocks" were identical in circuitry, signal levels and speed range to Laboratory Modules but had a higher packing density and fixed backplane wiring. They were used for computers, memory testers and other complex systems of logic.

 July:
By the end of its first fiscal year, Digital sells $94,000 worth of laboratory and systems modules and has 60 employees.
Here, Quality Control technicians test Laboratory and Systems Modules.

1959

Design work begins on DIGITAL Memory Test Systems.
From a Digital technical report dated March 1960:
"DEC1500 series memory testers -- complete systems for testing coincident current core memories under simulated computer conditions. DEC memory testers will test planes up to 64 by 64 with several patterns of information quickly and completely in a single operation."

The 3000 series Laboratory Modules and 4000 series Systems Modules go on the market. The 3000 series Laboratory Modules ran at 500 kHz. The 4000 series Systems Modules ran at 1 MHz and were principal components in the PDP-4 and PDP-5. Shown here are the modules in place in a PDP-4.

August:
Design work begins on Digital's first computer, the Programmed Data Processor-1 (PDP-1). A young hardware engineer named Ben Gurley was hired to design DIGITAL's first computer. Three and a half months later, the prototype Programmed Data Processor-1 (PDP-1) was complete. In December, the prototype was demonstrated at the Eastern Joint Computer Conference in Boston.

1960

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 $1,292,873 in 2025). 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.

The 5000 series Laboratory Modules and 6000 series Systems Modules go on the market. DIGITAL's 5000 and 6000 series modules were made possible by the arrival of a new series of transistors. This second generation of modules ran at 10 MHz, compared to the first generation modules which ran at 5 MHz.

The first DIGITAL Logic Handbook is published.
The Logic Handbook was an early project of Barbera Stephenson, the first woman hired as an engineer at DIGITAL. The Logic Handbook was the first in a long series of handbooks that worked both as textbooks and promotional tools. DIGITAL sent them to every customer and handed them out at trade shows.

November:
The PDP-1, the world's first small, interactive computer is delivered to Bolt, Beranek and Newman (BBN), a computer consulting firm in Cambridge, Massachusetts.

From a technical bulletin on the PDP-1, dated March 1960: "...a compact, solid state general purpose computer with an internal instruction execution rate of 100,000 to 200,000 operations per second. PDP-1 is a single address, single construction, stored program machine with a word length of 18-bits operating in parallel on 1's complement binary numbers."

1961

Gordon Bell begins design work on the PDP-4.
The PDP-4 was aimed at applications with not many calculations, but rather the single manipulation of input and output, such as controlling a bakery or fleet of elevators. "As computers [like the PDP-4] become smaller and less expensive," said Bell, "they will take over some special system types...then the computer becomes a 'module' of the system."

DECUS, the DIGITAL Equipment Computer Users Society, meets for the first time at Hanscom Field in Bedford, Massachusetts.

DECUS evolved because engineers needed a forum to share information and computer programs for DIGITAL's first computer, the PDP-1. Founded on the idea of open exchange of information between user and manufacturer, DECUS has grown to be one of the largest users' groups in the computer industry, with a total membership of about 100,000 and 23 chapters worldwide. The DECUS logo is a stylized version of the PDP-1 "TYPE 30" point scope.

1962

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-4s were eventually sold, most to a customer base similar to the original PDP-1.

July:
Shipments begin of the PDP-4, DIGITAL's second 18-bit computer.
Similar in structure to the PDP-1, the PDP-4 used slower memory and different packaging to achieve a lower price of $65,000. Approximately 54 PDP-4s were sold in application areas as diverse as nuclear physics, production and stock control.

September:
The PDP-1 operating system, the world's first timesharing system, is written by engineers at MIT and BBN for the PDP-1.
The PDP-1 operating system's timesharing ability made interactive access to computers economically viable by allowing various users to share the computer simultaneously. Shown here is the PDP-1 installation at BBN.

Gordon Bell begins design work on the architecture for the PDP-5.
Bell based the PDP-5 on a 12-bit digital controller (the DC-12) that DIGITAL had designed in 1961 but never built. Bell specified the instruction set in the fall of 1962. Design work was continued by Edson deCastro in early 1963. Shown here is the 7th PDP-5 built.

1963

The 8000 series modules are introduced.

The 8000 series modules, also known as VHF modules, ran at 30 MHz. The modules were used to build high performance systems. The technology developed in the VHF modules was used in the timesharing capabilities of the PDP-6. Shown here is a PDP-6 during testing.

DIGITAL's first 12-bit machine, the PDP-5, is announced.
The PDP-5 was innovative in replacing the radial structure of earlier designs with an I/O bus. By allowing peripheral equipment to be added incrementally -- rather than preallocating space, wiring and cable drivers -- the I/O bus design lowered the base costs of the system and simplified the configuring of machines in the field.

DIGITAL has 12 field service engineers who work together to cover a territory that includes the U.S. and installations in Germany and England.
In March, DIGITAL opened its first European sales and service office with three people in Munich, Germany. At the same time, the first Canadian sales office opened with two people in Ottawa.

1964

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 machine for which the Unix operating system was originally written. Unix ran only on DEC systems until the Interdata 8/32.

Flip Chip modules are developed.
Flip Chip modules were built of discrete transistors, diodes, resistors and capacitors. The series was designed so that backplanes could be wire-wrapped automatically, reducing costs and increasing production line throughput.
Flip Chips became the basis for the PDP-8.

October:
Digital unveils its first 36-bit computer, the PDP-6.
The PDP-6 was DEC's first "big" machine. It used 36-bit words, in common with other large computers at the time from companies like IBM, Honeywell and General Electric. Unlike those machines, the PDP-6 was supplied with a timesharing system "out of the box". Timesharing had been available for other machines, most famously the PDP-1 at Project MAC, but the PDP-6 was the first such system to be supported by the manufacturer.
Worldwide, only 23 PDP-6's were sold

Tops 10 is developed as the major user software interface for Digital's 36-bit machines. Tops 10 was developed from a 6-K word monitor for the PDP-6. It included user files and I/O device independence, a command control program and multiprocessing capabilities. Here an operator programs a PDP-6 using papertape.

December:
The PDP-7, Digital's third 18-bit computer, is introduced.
A successor to the PDP-4, the PDP-7 used smaller, more conventional system units and was well received in laboratory and data acquisition applications. The machine featured DIGITAL's first mass-storage based operating system (DECsys for DECtape). Ultimately, 120 PDP-7s were produced and sold.

DECtape is introduced concurrent with the PDP-7.
DECtape was a random access, block addressable medium for storing information on small magnetic tape. For the first time, tape was divided into sectors so that it could be used as an I/O storage system that was both interactive and inexpensive.

December:
DIGITAL is issued its first patent, for magnetic core memory. The inventors are Ken Olsen and Dick Best.
By 1971, Digital was the largest consumer of magnetic core memories other than IBM. Digital built its own magnetic core manufacturing business and by the mid-1970s was producing 30 billion magnetic cores per year.

1965

The PDP-7A is introduced.
The PDP-7A, a second version of the PDP-7, used the newly annouced R series Flip Chip modules. The machine pictured was built for Concord Control Corporation.

April:
Introduction of the PDP-8, the world's first mass-produced minicomputer.
On March 22, 1965, DEC introduced the PDP-8, which replaced the PDP-5's modules with the new R-series modules using Flip Chips. The machine was re-packaged into a small tabletop case, which remains distinctive for its use of smoked plastic over the CPU which allowed one to easily see the logic modules plugged into the wire-wrapped backplane of the CPU. Sold standard with 4 kWords of 12-bit core memory and a Teletype Model 33 ASR for basic input/output, the machine listed for only $18,000. The PDP-8 is referred to as the first real minicomputer because of its sub-$25,000 price.[36][37] Sales were, unsurprisingly, very strong, and helped by the fact that several competitors had just entered the market with machines aimed directly at the PDP-5's market space, which the PDP-8 trounced. This gave the company two years of unrestricted leadership,[38] and eventually 1450 "straight eight" machines were produced before it was replaced by newer implementations of the same basic design.[39]

November:
In what is believed to be the earliest example of around-the-world networking, a link is made by operating a PDP-6 in Perth, Australia from Boston via a telex link.

1966

Last update 01-03-2026 ... to be continued ...