Digital Equipment Corporation
Digital Equipment Corporation was an
American pioneering company in the
computer industry. It is often referred to within the computing industry as
DEC. (This acronym was once officially used by Digital itself,
[1] but the official name was always DIGITAL.) Its PDP and VAX products were arguably the most popular mini-computers for the scientific and engineering communities during the 70s and 80s. DEC was acquired by
Compaq, which subsequently merged with
Hewlett-Packard. As of
2006 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.
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 $60,000 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 at the time. 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" (flip flops, gates, transformer drivers, etc.) that could be combined together to run scientific and engineering experiments. In
1959 Ben Gurley started design of their first computer, the
PDP-1 (PDP being an initialism for
Programmable Data Processor).
|
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 up in a pre-configured 19" 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 9 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
The
VT180 (codenamed "Robin") 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.
12-bit systems
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. The PDP-8 was small enough to fit on a cart. It was simple enough to be used for many roles, and they soon started being sold in huge numbers to new market niches, labs, railways, and all sorts of 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.
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), because
Ted Hoff while evaluating the
Busicom designed calculator chipset for production by Intel realized that the PDP-8 sitting in the corner of the room was far more powerful than these 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" for them that they 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. DEC immediately found itself behind in the industry transition to 8 bit bytes. The PDP-11 16 bit computer was architected 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 and was followed by higher performance models such as the 11/45 and 11/70. As improvements to
integrated circuits enabled the single chip microprocessor, 11's eventually were packaged in cases no larger than a modern
PC.
The PDP-11 systems supported several operating systems, including
Bell Labs' new
Unix operating system as well as DEC's
RSX and
RSTS. Both RSTS and Unix were 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 11/70's 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 to allow
timesharing, and some could support split Instruction & Data spaces for an effective virtual address size of 128KB and a physical address size of up to 4MB.
PDP operating systems were the model for many other operating systems.
CP/M used a similar command syntax, and even retained the awkward
PIP program which was used to copy programs which was dropped in
MS-DOS and
Windows NT, which succeeded
CP/M and
VAX/VMS. The use of switches would lead to the adoption of '\' for pathnames in
Windows compared to '/' in
UNIX.
18-bit systems
 |
One of the Computer History Museum's PDP-1 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.
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 problems DEC produced first 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 being sold as the
DECsystem-10 and
DECSYSTEM-20VAX systems
 |
A representative VAX-11/780 system configuration |
In
1976 DEC decided to extend the PDP-11 archtecture to 32 bits, creating the first 32-bit minicomputer which they referred to as a
super-mini. This was launched as the
VAX (Virtual Address eXtension) 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 8 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 cancelled their
"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.
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 they appeared to gain a feeling of invincibility, and branched out into software, producing products for almost every then "hot" niche. This included their 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 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 4.2
BSD-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 their own Unix (
OSF/1 AXP, later renamed Digital UNIX, and even later Tru64), and it began to advertise more aggressively. DEC was simply not prepared to sell into a crowded Unix market however, and furthermore 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 one was "almost" IBM compatible. All 3 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 word processing which 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, though this is now commonplace.
DEC was initially resistant to even supporting
MS-DOS, and did not produce a true
IBM-PC compatible computer for many years, though 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 90s. DEC later produced a range of true IBM-PC compatible computers, including the Venturis, Celebris and Digital PC desktop lines, the HiNote series of laptops and the Digital Server and Prioris ranges of servers.[
1]
Architecting Solutions
Beyond DECsystem-10/20, PDP, VAX and Alpha, Digital was well respected for its engineering design, such as DNA (Digital Network Architecture - predominately DECnet products) and DSA (Digital Storage Architecture - disks/tapes/controllers). For in-depth articles regarding Digital technologies, refer to the archived
Digital Technical Journal.
Closing DEC's business
In June of 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 [
2].
* 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 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 now sells 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.
Eventually, on
January 26,
1998, what remained of the company was sold to
Compaq. Compaq itself was acquired by
Hewlett-Packard in 2002. Hewlett-Packard now sells what were Digital's StorageWorks disk/tape products [
3], 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% 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 nor follows the erstwhile Digital culture of engineering predominance.
The digital.com domain name is now owned by Hewlett-Packard and redirects to their US website [
4].
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, FranceSome of the former employees of Digital's Research Labs include:
*
Leslie Lamport*
Jeffrey MogulSome of the work of the Research Labs was published in the
Digital Technical Journal, published until 1998. At least some of the research reports are available online at [ftp://ftp.digital.com/pub/DEC/ ftp.digital.com], in the subdirectories WRL, SRC, NSL, CRL, PRL (see above)
(verified July 2006)Digital supported the
ANSI standards, especially the
ASCII character set, which survives in
Unicode and the
ISO character set. Digital's own
Multinational Character Set also had a large influence on the
Latin-1 characters in
ISO 8859-1 and
Unicode.
The first versions of the
C programming language and the
UNIX system ran on Digital's
PDP series of computers (first on a PDP-7, then the PDP-11's), which were the first commercially viable
minicomputers.
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.
Digital produced top-line operating systems, like
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 (as of
2004) to control and monitor factories, transportation systems and nuclear plants. Digital was an early champion of
time-sharing systems, as anybody who has used other operating systems like
MVS or
VM/CMS from
IBM can attest.
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 OSes that put it together in a complete and definitive form. The command-line interfaces found in the Digital's OSes, eventually to be 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 pre-Internet networks,
DECnet, which mixed 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 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".
Clustering, an operating system technology that treated multiple machines as one logical entity, was invented by Digital. Clustering permitted sharing of pooled disk and tape storage via the HSC50/70/90 and later series of Heirarchical Storage Controllers. HSC's 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 lead to the demise of Teletype Corporation.
The
VT100 computer terminal became the industry standard, and even today terminal emulators such as
HyperTerminal,
PuTTY and
Xterm still emulate a VT100 (though most actually emulate 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, the operating system guru 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). Cutler has never directly confirmed this but does not deny it either.
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,
dec.com (registered in 1985[
5]) being one of the first of the now ubiquitous
.com domains, and the first computer vendor to open a public website, on
October 1,
1993 [
6]. The popular
AltaVista, created by Digital, was one of the first comprehensive Internet
search engines (although
Lycos was earlier, it was much more limited).
Invention of
Digital Linear Tape (DLT) which began as a 5.25" replacement for a refrigerator sized 1600 bpi 1/2" 50 megabyte tape drive and grew to capacities in excess of 30 gigabytes.
Working 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).
The
iPaq PDA was created in the DEC's Western Research Lab, originally it was called
Itsy.
* "DEC used by Digital itself:"
PDP11 Processor Handbook (1973): page 8, "DEC, PDP, UNIBUS are registered trademarks of Digital Equipment Corporation;" page 1-4, "Digital Equipment Corporation (DEC) designs and manufacturers many of the peripheral devices offered with PDP-11's. As a designer and manufacturer of peripherals, DEC can offer extremely reliable equipment... The LA30 DECwriter, a totally DEC-designed and built teleprinter, can serve as an alternative to the Teletype."
* 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.
