Date: 03/04/1987On March 4, 1987, Prime Computer registered the domain name, making it 65th .com domain ever to be registered.

Prime Computer, Inc. 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 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, PC DOS, etc.).

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 32KB to 512 KB and from 6MB of Pertec 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 microcode-supported virtual memory capability. The virtual memory was simpler than used in later systems. Addresses were 16 bits, with each of up to 32 time-sharing (time slice) users, receiving a virtual 64K word address space. It had S-mode and R-mode instructions.

An example of the Prime 300 was installed in the mathematics department of the University of Aston in Birmingham, UK and at the Medical University of Hannover, Germany.

1976: Prime 400

The Prime 400 ran at 0.5 MIPS, had a main store of up to 8MB 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 up 2MB 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 2-8MB 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 Rensselaer Polytechnic Institute (RPI), Rutherford Appleton Laboratory (RAL), University of Paisley, Leeds University, Scripps Institution of Oceanography (SIO), University of Rhode Island, University of Manchester Institute of Science and Technology (UMIST), and the CADCentre in Cambridge.

PRIMENET and the local area network software RINGNET were announced.

1980: Prime 150 and 250

1981: Prime 850 (dual CPU machine)

Prime also marketed MEDUSA CAD Software

1982: Prime 2250 also known internally as “Rabbit”

1984: Prime 2550, 9650, 9750

1985: Prime 9955, 9655, 2655

The 9955 ran at 4.0 MIPS, had 8-16MB of memory and 2.7GB of disc storage and a 9 track tape unit. Five Prime 9955 computers ( to .syse, connected to JANET) were installed at the University of Salford (along with other systems such as the 2250, 2550, and 750); 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

By 1987 Prime Computer had introduced an alternative line of Intel 80386-based computers, the EXL-316 series, running the Unix operating system.

The company was successful in the 1970s and 1980s, peaking in 1988 at number 334 of the Fortune 500. In 1985 the company was the 6th largest in the minicomputer sector, with estimated revenues of US $564 million.  Much of this was based on the US Banking industry where the Pr1me Info database was widely accepted.

As of later 1989, Surrey University had the largest Prime Site in Europe, having multiple copies of virtually 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). Design engineers used PDGS for auto body design, and finite element analysis using NASTRAN. 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), (Cologne) Germany, (Dunton) England and (Geelong) Australia. The creators of PDGS, located in building #3 of Ford’s 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 Cambridge Interactive Systems (CIS), and having experience in the domain, the company explored transitioning to a CAD company. It embarked on a project headed by Vladimir Geisberg 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 a supposedly parameter driven CAD system called ProEngineer. Computervision acquired Cambridge Interactive Systems in 1983, and Prime independently developed their own version of MEDUSA.

Prime subsequently purchased Computervision and Vladimir Geisberg, then VP for CAD, tried to merge back together the Prime and Computervision versions of the Medusa CAD system, and to launch Prime Design. As time passed it became clear that Prime Design, while leading edge in theory, was totally unsuitable for real engineering design work. Prime Design was canned and Vladimir Geisberg was sacked in 1990 having failed to launch a viable CAD product and having destroyed the development organization for the ongoing Medusa CAD product.

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. The computer design and manufacturing portions of the company were shut down and the company was renamed Computervision. In 1992, Computervision sold Prime Information to Vmark Corporation. In 1998, it was bought by Parametric Technology Corporation. The remainder of the company became a support organisation for existing customers.


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 CDCs. In addition, the PRIMOS operating system would run unaltered across all Prime platforms; from the 2250 up to 750 (what would be considered today as a server). 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.