Prime Computer

Prime Computer

Prime Computer was a Natick, Massachusetts-based producer of minicomputers from 1972 until 1992. The alternative spellings "PR1ME" and "PR1ME Computer" were used as brand names or logos by the company.


The company was started by 7 founders, some of whom worked on the Multics project at MIT.

  • Robert Baron (President)
  • Sidney Halligan (VP Sales)
  • James Campbell (Director of Marketing)
  • Joseph Cashen (VP Hardware Engineering)
  • Robert Berkowitz (VP Manufacturing)
  • William Poduska (VP Software Engineering)
  • John Carter (Director of Human Resources)

The company started with the motto "Software First".

Poduska left in 1980 to start Apollo Computer.


The original products were clones of the Honeywell 316 and 516 minicomputers.

  • 1972: Prime 200

The first Prime system, similar to the DDP 516 but a 32-bit machine with paging. It ran an operating system called DOS, also referred to as PRIMOS 2 (not to be confused with MS DOS).

  • 1973: Prime 100

The Prime 100 was a stripped down version of the Prime 200 (no memory parity or floating point).

  • 1974: Prime 300

The Prime 300 had a main store of 128 KB and 6MB of disc storage. It ran DOSVM operating system, also referred to as PRIMOS 3, but still used earlier DOS for booting. One of the first minicomputers with virtual memory capability. The virtual memory was simpler than used in later systems. Addresses were 16 bits, with a 64K address space. Multiple 64K address spaces were allowed. It had S-mode and R-mode instructions.

An example was installed in the mathematics department of the University of Aston in Birmingham, UK.

  • 1976: Prime 400

The Prime 400 ran at 0.5 MIPS, had a main store of 192KB and 160MB of disc storage. The name PRIMOS was now used for the operating system and the P400 ran PRIMOS 4. It ran a V-mode instruction set, along with the S-mode and R-mode instructions. It had a segmented virtual memory architecture, somewhat similar to Multics.

  • 1979: Prime 450, 550, 650 ,750

The Prime 550 was an upgrade in performance over the Prime 400. It ran at 0.7 MIPS, had 1MB of memory and 500MB of disc storage and a 9 track tape unit.

The Prime 750 was a major upgrade. It ran at 1.0 MIPS, had 2-4MB of memory and 1200MB of disc storage and a 9 track tape unit. This was very competitive with a similarly priced DEC VAX-11/780 and was one of the first 32-bit superminicomputers. Prime 750 systems were installed at Rutherford Appleton Laboratory (RAL) and University of Manchester Institute of Science and Technology (UMIST).

PRIMENET and the local area network software RINGNET were announced.

  • 1980: Prime 150 and 250
  • 1981: Prime 850

Prime also marketed MEDUSA CAD Software

  • 1982: Prime 2250 aka internally as "Rabbit"
  • 1984: Prime 2550, 9650, 9750
  • 1985: Prime 9955, 9655, 2655

The 9955 ran at 4.0 MIPS, had 8-12MB of memory and 2700MB of disc storage and a 9 track tape unit. A Prime 9955 was installed at UMIST and a Prime 9655 at Nottingham University.

  • 1986: Prime 2350, 2450, 9755, and 9955-II
  • 1987: Prime 2455, 2755, 6350, and 6550

The company was successful in the 1970s and 1980s, peaking in 1988 at number 334 of the Fortune 500.

As of later 1989, Surrey University had the largest Prime Site in Europe, having virtually multiple copies of every 50 series machine (mostly running Primos 20.x, but some still running 19.x).

Prime was heavily involved with Ford’s internal computer-aided design (CAD) product, Product Design Graphics System (PDGS). It used a vectorscope from Lundy for a display. At one time in 1980s it was the world largest integrated CAD system, spanning the US, Japan (Mazda was Ford's subsidiary/partner), and Germany. The creators of PDGS, located in building #3 of Fords Dearborn design headquarters, began working on the concept of parametrically driven geometry, which led to a PRIMEDesign system.

The company also had marketing rights to the MEDUSA CAD system, produced in England by a company named Cambridge Interactive Systems, and experience in the domain, the company explored transitioning to a CAD company. It embarked on a project to build a CAD-CAM system of its own called PRIMEDesign. This product was to compete with the industry leader at that time, CADDS4 from Computervision. RISC processors from MIPS Technologies and graphics processors from Silicon Graphics created the platform for PRIMEDesign as well as being the genesis of modern day SGI. During this period, in 1985, Sam Geisberg left Computervision to found Parametric Technology Corporation and produce the first parameter driven CAD system called ProEngineer. Computervision acquired Cambridge Interactive Systems in 1983, and Prime forked their own version of MEDUSA.

By the late eighties, the company was having problems retaining customers who were moving to lower-cost systems. In addition, Prime was failing to keep up with the increasing customers' need for raw computing power. By the end, not a single Prime computer was subject to COCOM export controls, as they were insufficiently powerful for the US Government to fear their falling into the hands of hostile powers.

Ultimately, Prime tried to improve its CAD presence by purchasing several CAD companies including Computervision in 1989 for $300 million. PRIMEDesign and CADDS were combined to form a new product called CADDS5. The purchase left the company vulnerable to a hostile take-over, and such attempt was made by Bennett S. LeBow's MAI Basic Four corporation. To fend off the take-over, the company was bought back into private ownership by New York venture capitalist, J.H. Whitney. The computer design and manufacturing portions of the company were shut down and the company was renamed Computervision. In 1998 it was bought by aforementioned Parametric Technology Corporation, that exists to this day.

Operating System

The company operating system, PRIMOS was originally written mostly in the Fortran IV programming language with some assembler. Subsequently the PL/P and Modula-2 languages were used in the Kernel. A number of new PRIMOS utilities were written in SP/L which was similar to PL/P.

Prime 300 Specification

  • A microprogrammed 16-bit central processor with floating point hardware, error detection and system integrity checking features.
  • 128K byte, 600 nanosecond access MOS main memory.
  • 6MB cartridge disk. 165 cps character printer.
  • System software including a disk operating system and FORTRAN, BASIC and Assembly languages.
  • support for up to 31 users for a total purchase price of about US$165,000

Specialised Software

General Business

Office Automation System

Prime acquired the OAS application from its developer, ACS America Inc., a now-defunct New York City software house.

It was one of the pioneer systems, and fought hard to win a place in the UK DTI Office Automation Pilot sites, but failed to achieve it.

OAS consisted of:

  • electronic mail, initially restricted to a single, non networked minicomputer, only much later released into a synchronised global directory system, albeit only functioning with Prime to Prime networks
  • word processing, either on dumb terminals like the PT25, PT45 and PST100, or on the partially intelligent PT65 terminal which had to download its WP software from the host minicomputer whenever it was turned on, and was a "page based" word processing system. Such an intelligent workstation concept is very Wang-like, but the execution was far slower than Wang's dual co-ax 928 link since it was over standard RS232C cabling runs. The word processing was not of the highest quality, and the PT65 was subject to software errors that scrambled the documents being worked on.

Prime also claimed that OAS provided automatic translation between languages, but the feature was mostly non-existent, consisting only of one-word-at-a-time lookup in small dictionaries for Spanish and Norwegian.

Recognising the drawbacks of the downloadable WP workstation, Prime formed an agreement with Convergent Technologies for their AWS which Prime named the "Prime Producer 100" (launched in mid 1983) and later for Convergent's modular NGEN, clip together system, the "Prime Producer 200" (launched in 1984), each of which had far superior WP to the initial Prime offering, and were document based.

In the UK Prime had a very active OAS User Group whose suggestions were acted upon in new product development. UK Pioneers of the system included the London Docklands Development Corporation and Oxford Polytechnic, now Oxford Brookes University.

Prime Information

Very similar in concept and execution to the Pick environment developed by Richard Pick, Prime Information allowed rapid, 4GL or 4GL-like development of applications around relational or quasi relational database structures. After a series of evolutions Prime Information was acquired by IBM corporation. It became part of IBM's U2 product family. The former Prime Information is now known as IBM UNIVERSE. Further information can be found at

Prime Information Connection

In (approx) 1984 Prime developed a system to conflict with OAS and confuse the market. Prime Information Connection added word processing to Prime Information, giving the company two office oriented suites to offer in a marketplace dominated by Wang Laboratories


Prime originally entered the CAD industry through Ford. At the time Ford was using Control Data Corporation (CDC) stand-alone computers. Data was shared via reel tape and stored in “Data Collector” rooms at each facility. Ford began looking for a small computer that had all the advantages of the CDC computers, but could also connect to a network.

Prime’s 2250 (“Rabbit”) offered the combination Ford was looking for in a package smaller than the original CDC’s. In addition, the PRIMOS operating system would run unaltered across all Prime platforms; from the 2250 up to the (what would be considered today as a server) 750. As a result, the Data Collector (rooms) would contain several 750 class machines, each with rows of CDC 300 or 600MB drives. Primenet (token ring) network connected all CAD stations in a building with its Data Collector.

Ford pushed PDGS out to its suppliers and engineering contractors throughout the northern Midwest.

Prime gained expertise over the years with its collaboration with Ford and continued to expand into the CAD market with its Medusa product. With the acquisition of ComputerVision, Prime appeared to be a formidable force in the CAD/CAM industry.

Prime Medusa versions 5 and CV Medusa 7 were merged/recombined into a product that was called Medusa version 12.

Prime also picked up Calma CAD systems from GE.

Encoding Header Field for Internet Messages

Developed on, which was the hub that relayed global electronic mail for Prime Computer. The software used on this computer system, PDN Mail, developed by Robert Ullmann, it was designed to use the encoding header field that was later explained in a RFC. PDN Mail was years ahead of its time and was also used by Microsoft Corporation until MIME was introduced.

Before MIME existed, PDN Mail was able to perform the same functions and was used to send software updates as well as all sorts of attachments between systems. In August 1993, Robert Ullmann, David Robinson and Al Costanzo, wrote RFC 1505. This RFC, documented the Encoding Header Field for Internet Messages that PDN mail used and was published by the RFC editor, Jon Postel that same year.


A series of memorable advertisements from 1980 featured actors Tom Baker and Lalla Ward as their characters from the TV series Doctor Who. All four of these adverts have since been included on the DVD of the Destiny Of The Daleks serial in which both actors appear.

Another series of advertisements featured a C-3PO-like robot called Albert EinPrime.

External links

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