Digital Equipment Corporation

Digital Equipment Corporation

File:Digital dec logo.png
Founded	1957
Defunct	1998
Fate	Assets were sold to various companies. What remained was sold to Compaq.
Successor	Compaq
Headquarters	Maynard, Massachusetts United States
Key people	Ken Olsen (founder and CEO) Harlan Anderson (co-founder)
Products	PDP VAX DEC Alpha
Number of employees	over 100,000 (1980s)

Digital Equipment Corporation was a pioneering American company in the computer industry. It is often referred to within the computing industry as DEC. (This acronym was frequently officially used by Digital itself, but the official name was always DIGITAL.) Its PDP and VAX products were arguably the most popular minicomputers for the scientific and engineering communities during the 1970s and 1980s. DEC was acquired by Compaq in June 1998, which subsequently merged with Hewlett-Packard in May 2002. As of 2007 its product lines were still produced under the HP name. From 1957 until 1992 its headquarters was in an old woolen mill in Maynard, Massachusetts.

Digital Equipment Corporation should not be confused with Digital Research; the two were unrelated, separate entities; or with Western Digital (despite the fact that they made the LSI-11 chipsets used in Digital Equipment Corporation's low end PDP-11/03 computers). Note, however, that there were Digital Research Laboratories where DEC did its corporate research.

History

The company was founded in 1957 by Ken Olsen and Harlan Anderson, two engineers who had been working at MIT Lincoln Laboratory on the TX-2 project. The TX-2 was a transistor-based computer using the then-huge amount of 64K 36-bit words of core memory. When that project ran into difficulties, Olsen and Anderson left MIT to form DEC. Venture capital of about $70,000 was provided by Georges Doriot and his American Research and Development Corporation. AR&D later sold its investment in Digital for approximately $450 million, certainly the best VC return ever to that point. At the time, the VC market was hostile to computer companies, and investors shied from their plans. The original business plan named the company "Digital Computer Corporation," but AR&D required that the name be changed to DEC. Instead, DEC started building small digital "modules" such as flip flops, gates, and transformer drivers that could be combined to run scientific and engineering experiments. In 1959, Ben Gurley started design of the company's first computer, the PDP-1 (PDP being an initialism for Programmable Data Processor as a means of attracting VC funding. As he put it, "We aren't building computers, we're building 'Programmable Data Processors'." DEC began operations in a Civil War era textile mill in Maynard, Mass., where plenty of inexpensive manufacturing space was available.

System Building Blocks 1103 hex-inverter card (both sides)

The first modules were the free-standing "laboratory modules," placing one or two gates inside an extruded aluminum housing. These modules could be stacked in a preconfigured 19-in rack shelf that supplied power to the modules; the logic circuits were then established using banana plug patch cords installed at the front of the modules. The same circuits were then packaged as "System Building Blocks," which were used to build the PDP-1.

A "B" (blue) series Flip Chip module containing nine transistors, 1971

The same circuits were then packaged as the first "R" (red) series "Flip-Chip®" modules. Later, other module series provided additional speed, much higher logic density, and industrial I/O capabilities. Digital published extensive data about the modules in free catalogs that became very popular.

8-bit systems

In the 1980s, DEC built the VT180 (codenamed "Robin"), which was a VT100 terminal with a Z80-based microcomputer running CP/M.

This evolved into the Rainbow 100, which had both Z80 and 8088 CPUs and was capable of running CP/M, CP/M-86, and MS-DOS.

DEC also used Intel 8-bit microprocessors as embedded processors within larger systems; for example, as the console processor in PDP-11/04, 11/34, and 11/44 systems and as the main processor within the VT100 family of video terminals.

12-bit systems

A PDP-8 on display at the Smithsonian's National Museum of American History in Washington, D.C.. This example is from the first generation of PDP-8s, built with discrete transistors and later known as the Straight 8.

To serve laboratories at a lower cost, DEC provided the PDP-5, an early minicomputer, in 1963. True success followed with the introduction of the famous PDP-8 in 1964. It was a smaller, 12-bit word machine that sold for about $16,000 and was small enough to fit on a cart. The device was simple enough to be used for many roles, and was soon being sold in large quantities to new market niches such as labs, railways, and various industrial applications.

The PDP-8 was important historically because it was the first computer that was regularly purchased by a handful of end users as an alternative to using a larger system in a data center. Because of their low cost and portability, these machines could be purchased to fill a specific need, unlike the mainframe systems of the day that were nearly always shared among diverse users. Today, the PDP-8 is generally regarded as the first minicomputer. The PDP-8 spawned a cousin, the PDP-12, which merged data acquisition and display capabilities developed with the NIH-sponsored LINC computers into the PDP-8 architecture.

The PDP-8 was used as the "brains" for many specific scientific and research projects. Once such adaptation was the "Durrum Instruments D-500 Amino Acid Analyzer" wherein a PDP-8 was used for process control.

Many 8- and 16-bit machine architectures are said to be inspired by the PDP-8, including the HP 2100 and Data General Nova, and to a lesser extent the National Semiconductor IMP, PACE, and INS8900 microprocessors and the Signetics 2650 microprocessor. Machines based on the PDP-8 can be characterized by a small number of accumulators (such as AC and MQ, or A and B), or a small number of general registers (R0-R3) rather than a relatively large number of regular registers (such as R0-R7 or R15), and by memory addressing in terms of a base page and a current page (related to PC value).

The design of the 4 bit Intel 4004 was also inspired by the PDP-8, although it has a series of regular registers (R0-R15). While evaluating the Busicom designed calculator chipset for production by Intel, Ted Hoff realized that the PDP-8 sitting in the corner of the room was far more powerful than newer chips, yet the circuitry was much simpler. Therefore, he proposed that Intel not make the chips designed by Busicom, but instead design a "computer chipset" that buyers could program as a calculator.

16-bit systems

Data General was formed by a group of DEC engineers in May, 1968, and rapidly brought the 16-bit NOVA minicomputer to market, based on a proposed architecture that DEC management had rejected. DEC immediately found itself behind in the industry transition to 8-bit bytes. The PDP-11 16-bit computer was designed in a crash program by Harold McFarland, Gordon Bell, Roger Cady, and others. Its numerous architectural innovations, including the UNIBUS, proved superior to all competitors and the "11" architecture was soon the industry leader. The first model was the PDP-11/20, which was followed by higher performance models such as the 11/45 and 11/70. When improvements to integrated circuits enabled the single-chip microprocessor, 11s eventually were packaged into systems no larger than a modern PC.

The PDP-11 supported several operating systems, including Bell Labs' new Unix operating system as well as DEC's DOS-11, RSX-11, IAS, RT-11, and RSTS/E. Many early PDP-11 applications were developed using standalone paper-tape utilities. DOS-11 was the PDP-11's first disk operating system, but was soon supplanted by more capable systems. RT-11 provided a practical real-time operating system, allowing the PDP-11 to continue Digital's critical role as a computer supplier for embedded systems. RSX provided a general-purpose multitasking environment and supported a wide variety of programming languages. IAS was a time-sharing version of RSX-11D. Both RSTS and Unix were time-sharing systems available to educational institutions at little or no cost, and these PDP-11 systems were destined to be the sandbox for a generation of engineers and computer scientists. Large numbers of 11/70s were deployed in telecommunications and industrial control applications. AT&T became DEC's largest customer.

The PDP-11's 16-bit byte-oriented architecture provided a 64KB virtual address space. Most models had a paged physical memory architecture and memory protection features, useful for multitasking and time-sharing, and some supported separate Instruction & Data spaces for an effective virtual address size of 128KB within a physical address size of up to 4 MB.

Another significant innovation of the PDP's architecture (PDP-11 in particular, but also to some degree the other PDPs) was that all peripheral device interfaces were memory mapped: rather than using special I/O instructions to work with peripherals, programmers accessed device registers by reading and modifying the contents of specific physical memory addresses.

PDP operating systems were the model for many other operating systems. CP/M used a command syntax similar to RT-11's, and even retained the awkward PIP program used to copy other programs. DEC's use of '/' for "switches" (command-line options) would lead to the adoption of '\' for pathnames in Windows as opposed to '/' in Unix.

18-bit systems

Through the 1960s, DEC produced a series of machines aimed at a price/performance point below IBM's mainframe machines, typically based on an 18-bit word using core memory: the PDP-1, the PDP-4 (1963), the PDP-7 (the first to use their Flip-Chip® technology) and PDP-9 (1965), and finally the PDP-15 series (starting in 1970 and later sold as the "XVM" series). The PDP-15 was an early user of TTL integrated circuits. These computers were moderately powerful computers for their time, mainly used in industrial, scientific, and medical laboratories.

24-bit systems

According to Gordon Bell, the second PDP (PDP-2) was reserved for a 24-bit computer that was never developed.

32-bit systems

In addition to the VAX below, DEC collaborated with ARM Limited to produce the StrongARM processor. This processor, based in part on ARM7 and in part on DEC technologies like Alpha, was highly compatible with the ARMv4 architecture and set the standard for microprocessors intended for mobile applications, virtually destroying the market for technologies such as MIPS and SuperH in these markets. Microsoft subsequently dropped PocketPC support for these architectures, largely as a result of the extremely broad appeal of StrongARM. When DEC ceased to trade, the StrongARM intellectual property was sold to Intel, who continued to manufacture StrongARM, as well as developing it into XScale.

36-bit systems

A paper design for the third PDP (PDP-3) was developed and a single computer was produced from the specification by a DEC customer using DEC System Building Blocks.

For larger scientific applications DEC produced the PDP-6 in 1964, using a 36-bit architecture. Using the same word length as the IBM 701-7094 series scientific computers, which were being replaced by the 32-bit IBM System/360 series, and the UNIVAC 1107, which was replaced by the successor UNIVAC 1108 the next year, provided an alternative growth path for scientific customers. The successor was the PDP-10 series, eventually sold as the DECsystem-10 and DECSYSTEM-20.

One of the most unusual peripherals produced for the PDP-10 was the DECtape. The DECtape was a length of standard magnetic tape wound on 5-in reels. However, the recording format was a 10-track approach using fixed-length numbered 'blocks' organized into a standard file structure, including a directory. Files could be written, read, changed and deleted on a DECtape as though it were a hard drive. In fact, some PDP-10 systems had no hard drives at all, using DECtapes alone for their primary data storage. For greater efficiency, the DECtape drive could read and write to a DECtape in both directions.

VAX and Ethernet systems

File:Vax780 small.jpeg

A representative VAX-11/780 system configuration

In 1976, DEC decided to extend the PDP-11 architecture to 32 bits, creating the first 32-bit minicomputer, referred to as a super-mini. This was launched as the Virtual Address eXtension (VAX) 11/780 in 1978, and immediately took over the vast majority of the minicomputer market. Desperate attempts by competitors such as Data General (which had been formed in 1968 by Ed DeCastro and eight other DEC engineers who had worked on a 16-bit design that DEC had rejected) to win back market share failed, due not only to DEC's successes, but the emergence of the microcomputer and workstation into the lower-end of the minicomputer market. In 1983, DEC canceled its "Jupiter" project, which had been intended to build a successor to the PDP-10, and instead focused on promoting the VAX as their the single computer architecture for the company. It was believed that microprocessor technology at the low end and networking of larger systems could produce a 1:1000 range of computing power from one architecture.

The VAX series had an instruction set that is rich even by today's standards (as well as an abundance of addressing modes). In addition to the paging and memory protection features of the PDP series, the VAX supported virtual memory. The VAX could use both Unix and DEC's own VMS operating system.

In 1984, DEC launched its first 10 Mbps Ethernet. Ethernet allowed scalable networking, and VAXcluster allowed scalable computing. Combined with DecNet and Ethernet based terminal servers (LAT), DEC had produced a networked storage architecture which allowed them to compete directly with IBM. The Ethernet replaced the IBM token-ring, and went on to become the dominate networking model for the remainder of the 20th century and beyond.

At its peak in the late 1980s, Digital was the second-largest computer company in the world, with over 100,000 employees. It was during this time that the company appeared to take on a feeling of invincibility, and it branched out into software, producing products for almost every "hot" niche at the time. This included Digital's own networking system, DECnet, file and print sharing, relational database, and even transaction processing. Although many of these products were well designed, most of them were DEC-only or DEC-centric, and customers frequently ignored them and used third-party products instead. This problem was further magnified by Olsen's aversion to traditional advertising and his belief that well-engineered products would sell themselves. Hundreds of millions of dollars were spent on these projects, at the same time that workstations based on RISC architecture were starting to approach the VAX in performance. Constrained by their huge success of the VAX/VMS products, which followed the proprietary model, the company was very late to respond to commodity hardware in the form of Intel-based personal computers and standards-based software such as Unix and Internet protocols such as TCP/IP. In the early 1990s, DEC found its sales faltering and its first layoffs followed. The company that created the minicomputer, a dominate networking technology, and arguably the first computers for personal use, did not effectively respond to the significant restructuring of the computer industry.

Alpha and MIPS systems

Inside view of AlphaServer 2100.

During the 1980s, DEC made several attempts at designing a RISC (reduced instruction set) processor to replace the VAX architecture. Eventually, in 1992, DEC launched the Alpha processor (initially named Alpha AXP, the "AXP" was later dropped). This was a 64-bit RISC architecture (as opposed to the 32-bit CISC architecture used in the VAX) and one of the first 64-bit microprocessor designs. The Alpha offered class-leading performance at its launch, and subsequent variants continued to do so into the 2000s. Alpha-based computers (the DEC AXP series, later the AlphaStation and AlphaServer series) superseded both the VAX architecture and the MIPS-based DECstation line, and could run VMS, DEC's 4.2BSD-based Unix variant called Ultrix and Microsoft's new server operating system Windows NT.

DEC tried to compete in the Unix market by marketing the VMS operating system as "OpenVMS" and by selling its own Unix (OSF/1 AXP, later renamed Digital UNIX and then Tru64), and began to advertise more aggressively. DEC was simply not prepared to sell into a crowded Unix market however, and the low end PC-servers running NT (based on Intel processors) took market share from Alpha-based computers. DEC's workstation and server line never gained much popularity beyond former DEC customers.

Personal computers

Digital responded to the challenge of the IBM-PC with not one, but three machines, tied to proprietary architectures. One machine was for "professionals," barely hiding CEO Ken Olsen's contempt for the IBM PC. One was for word processing only and another was "almost" IBM compatible. All three were commercial failures. Packaging was based on the new VT220 terminals. The DEC Professional Series Model 350 (380) was based on the PDP-11/23 (11/73)which, running RSX-11M+ derived the menu-driven P/OS, was software incompatible with the base of largely CP/M and 8080 based microcomputers. The 'Pro' provided 64K 16-bit addresses windowing into 2 MB of physical memory, compared to 1 MB capacity of the Intel 8086. The DecMate I and II was the latest version of the PDP-8 based word processors, but not really suited to general computing, nor competitive with Wang Laboratories word processing that was becoming popular. The Rainbow 100 ran an 8086 implementation of CP/M, so applications could in theory be recompiled; but, by this time, users were expecting custom-built applications such as Lotus 1-2-3, which was eventually ported along with MS-DOS V2.0 and introduced in late 1983. Users objected to having to buy preformatted floppy disks.

DEC was initially resistant to even supporting MS-DOS, and did not produce a true IBM-PC compatible computer for many years, although the VAXmate came close, introduced in 1986 along with MS-Windows V1.0 and a VAX/VMS based (file and print) server for Microsoft's network protocols (such as SMB and NetBIOS) along with integration into DEC's own DECnet-family, providing LAN/WAN connection from PC to mainframe (supermini). The lines of DECs personal computers peaked with the Alpha-based 64-bit RISC workstations introduced in the early 1990s. DEC later produced a range of true IBM-PC compatible computers, including the Starion, Venturis, Celebris and Digital PC desktop lines, the HiNote series of laptops and the Digital Server and Prioris ranges of servers.

Architecting Solutions

Beyond DECsystem-10/20, PDP, VAX and Alpha, Digital was well respected for its communication subsystem designs, such as Ethernet, DNA (Digital Network Architecture - predominantly DECnet products), DSA (Digital Storage Architecture - disks/tapes/controllers), and its "dumb terminal" subsystems including VT100 and DECserver products.

Closing DEC's business

In June 1992, Ken Olsen was replaced by Robert Palmer as the company's CEO. Palmer had joined DEC in 1985 to run Semiconductor Engineering and Manufacturing. His relentless campaign to be CEO, and success with the Alpha microprocessor family, made him a candidate to succeed Olsen. However, Palmer was unable to stem the tide of red ink. More rounds of layoffs ensued and many of DEC's assets were spun off:

• Worldwide training was spun off to form an independent/new company called Global Knowledge Network.
• Their database product, Rdb, was sold to Oracle.
• The TK-series tape technology was sold to Quantum Corporation as the basis for today's DLT and SuperDLT technology.
• Text terminal business (VT100 and its successors) was sold in August 1995 to Boundless Technologies.
• In March 1997, DEC's CORBA-based product, ObjectBroker, and its messaging software, MessageQ, was sold to BEA Systems, Inc.
• In May 1997, DEC sued Intel for allegedly infringing on its Alpha patents in designing the Pentium chips. As part of a settlement, DEC's chip business was sold to Intel. This included DEC's StrongARM implementation of the ARM computer architecture, which Intel sold as the XScale processors commonly used in Pocket PCs.
• In 1997, the printer business was sold to GENICOM (now TallyGenicom), which then produced models bearing the Digital logo.
• At about the same time, the networking business was sold to Cabletron Systems, and subsequently spun off as Digital Network Products Group.
• The DECtalk and DECvoice voice products were spun off, and eventually arrived at Fonix.
• RT-11 is now supported and distributed by the Mentec company.

Eventually, on January 26, 1998, what remained of the company (including Digital's multivendor global services organization and customer support centers) was sold to Compaq, which was acquired by Hewlett-Packard in 2002. Hewlett-Packard now sells what were Digital's StorageWorks disk/tape products, made possible through the Compaq acquisition.

The Digital logo survived for a while after the company ceased to exist, as the logo of Digital GlobalSoft, an IT services company in India (which was a 51 percent subsidiary of DEC). Digital GlobalSoft was later renamed "HP GlobalSoft" (also known as the "HP Global Delivery India Center" or HP GDIC) and no longer uses the Digital logo.

The digital.com and DEC.com domain names are now owned by Hewlett-Packard and redirect to their US website.

Research

DEC's Research Laboratories (or Research Labs, as they were commonly known) conducted Digital's corporate research. Some of them were operated by Compaq and are still operated by Hewlett-Packard. The laboratories were:

• Western Research Laboratory (WRL) in Palo Alto, California
• Systems Research Center (SRC) in Palo Alto, California
• Network Systems Laboratory (NSL) in Palo Alto, California
• Cambridge Research Laboratory (CRL) in Cambridge, Massachusetts
• Paris Research Laboratory (PRL) in Paris, France
• MetroWest Technology Campus (MTC) in Maynard, Massachusetts

Some of the former employees of Digital's Research Labs or Digital's R&D in general include:

• Gordon Bell
• Henry Burkhardt III, co-founder of Data General Corporation and Kendall Square Research
• Luca Cardelli
• Dave Cutler
• Ed deCastro, co-founder of Data General Corporation
• Henri Gouraud
• Jim Gray
• Alan Kotok
• Leslie Lamport
• Butler Lampson
• Jeffrey Mogul
• Louis Monier
• Brian Reid
• Paul Vixie

Some of the work of the Research Labs was published in the Digital Technical Journal, published until 1998.

Accomplishments

Digital supported the ANSI standards, especially the ASCII character set, which survives in Unicode and the ISO 8859 character set family. Digital's own Multinational Character Set also had a large influence on ISO 8859-1 (Latin-1) and, by extension, Unicode.

The first versions of the C programming language and the UNIX operating system ran on Digital's PDP series of computers (first on a PDP-7, then the PDP-11's), which were among the first commercially viable minicomputers, although for several years Digital itself did not encourage the use of Unix.

Digital also produced the popular VAX computer family, the first pure 64-bit microprocessor architecture, Alpha AXP, the first commercially successful workstation (the VT-78), and some commercially unsuccessful personal computers. The central computing system of the Soviet reusable Buran spaceship was based on two microVAX computers.

Digital produced widely used interactive operating systems, including OS-8, TOPS-10, TOPS-20, RSTS/E, RSX-11, RT-11, and OpenVMS. PDP computers, in particular the PDP-11 model, inspired a generation of programmers and software developers. Some PDP-11 systems more than 25 years old (software and hardware) are still being used to control and monitor factories, transportation systems and nuclear plants. Digital was an early champion of time-sharing systems.

Digital was to the command-line interface (CLI) what Apple was to the GUI: there was history before and innovation after, but it was Digital's operating systems that put it together in a complete and definitive form. The command-line interfaces found in Digital's systems, eventually codified as DCL, would look familiar to any user of modern microcomputer CLIs; those used in earlier systems, such as CTSS, IBM's JCL, or Univac's time-sharing systems, would look utterly alien. Many features of the CP/M and MS-DOS CLI show a recognizable family resemblance to Digital's OSes, including command names such as DIR and HELP and the "name-dot-extension" file naming conventions.

VAX and MicroVAX computers (very widespread in the 1980s) running VMS formed one of the most important proprietary networks, DECnet, which linked business and research facilities. The DECnet protocols formed one of the first peer-to-peer networking standards. Email, file sharing, and distributed collaborative projects existed within the company long before their value was recognized in the market.

Digital, Intel and Xerox through their collaboration to create the DIX standard, were champions of Ethernet, but Digital is the company that made Ethernet commercially successful. Initially, Ethernet-based DECnet and LAT protocols interconnected VAXes with DECserver terminal servers. Starting with the UNIBUS to Ethernet adapter, multiple generations of Ethernet controllers from Digital were the de facto standard. The CI "computer interconnect" adapter was the industry's first network interface controller to use separate transmit and receive "rings".

Digital also invented clustering, an operating system technology that treated multiple machines as one logical entity. Clustering permitted sharing of pooled disk and tape storage via the HSC50/70/90 and later series of Hierarchical Storage Controllers. HSCs delivered the first hardware RAID 0 and 1 capabilities and the first serial interconnects of multiple storage technologies. This technology was the forerunner to systems like Network of Workstations which are used for massively cooperative tasks such as web-searches and drug research.

The LA36 and LA120 dot matrix printers became industry standards and may have hastened the demise of the Teletype Corporation.

The VT100 computer terminal became the industry standard, implementing a useful subset of the ANSI X3.64 standard, and even today terminal emulators such as HyperTerminal, PuTTY and Xterm still emulate a VT100 (or its more capable successor, the VT220).

The X Window System, the first remote-windowing system, was developed by Project Athena at MIT. Digital was the primary sponsor for this project.

Dave Cutler, who led the development of RSX-11M, RSX-11M+, VMS and then VAXeln, left Digital in 1988 to lead the development of Windows NT. A rumor circulated for a long time that WNT=VMS+1 (increment each letter by one). In the early 1990's, when asked directly about this, Cutler quipped "What took you so long ?", leaving open the possibility that VMS becoming WNT was a very unlikely coincidence. However, as noted in the article on Windows NT, the order of events does not support this.

Notes-11 and its follow-on product, VAXnotes, were two of the first examples of online collaboration software, a category that has become to be known as groupware. Len Kawell, one of the original Notes-11 developers later joined Lotus Development Corporation and contributed to their Lotus Notes product.

Digital was one of the first businesses connected to the Internet with dec.com, registered in 1985, being one of the first of the now ubiquitous .com domains. gatekeeper.dec.com was a well-known software repository during the pre-World Wide Web days, but Digital was also the first computer vendor to open a public website, on October 1, 1993. The popular AltaVista, created by Digital, was one of the first comprehensive Internet search engines. (Although Lycos was earlier, it was much more limited.)

DEC invented Digital Linear Tape (DLT), which began as a 5.25" replacement for refrigerator-sized reel-to-reel ½" tape drives and grew to capacities in excess of 30 gigabytes.

Work on the first hard-disk-based MP3-player, the Personal Jukebox, started at the DEC Systems Research Center. (The project was started about a month before the merger into Compaq was completed.)

PDA concepts created in DEC's Western Research Lab, originally called Itsy, were incorporated into The iPaq which was developed as a successor to Compaq's own PDA, the Aero, originally developed to showcase WindowsCE using display and other technology from Nintendo color GameBoy.

Anecdotes

The first spam in computer history was sent in 1979 by a Digital employee. Over 400 people received his promotional message via the Arpanet network.

Notes and references

• Edgar H. Schein, Peter S. DeLisi, Paul J. Kampas, and Michael M. Sonduck, DEC Is Dead, Long Live DEC: The Lasting Legacy of Digital Equipment Corporation (San Francisco: Barrett-Koehler, 2003), ISBN 1-57675-225-9.

• C. Gordon Bell, J. Craig Mudge, and John E. McNamara, Computer Engineering - A DEC View of Hardware Systems Design; Digital Press, 1978, ISBN 0-932376-00-2.

• Alan R. Earls, Digital Equipment Corporation; Arcadia Publishing, 2004, ISBN 0-7385-3587-7.

External links

• OpenVMS.org
• Tru64.org (initially Ultrix, then OSF1, and then Digital UNIX)
• pictures of DEC chips at chipdb.org