Ridge Computers

Ridge Computers, Inc.
Company type	Private
Industry	Computer manufacturing
Founded	May 1980; 46 years ago
Founder	Edward J. Basart, Dave Folger, Ron Kolb, Hugh Martin, John Sell, Neil C. Wilhelm
Defunct	April 1990
Fate	Ceased operations
Headquarters	Santa Clara, United States
Area served	Worldwide
Key people	Dave Folger (President and CEO until 1986), Bob O. Evans (CEO), Michael Preletz (CEO)
Products	Deskside workstations, workgroup servers, superminicomputers, Ridge Operating System (ROS)
Number of employees	150 (mid-1980s)

Adapted from the English Wikipedia article Ridge Computers, available under CC BY-SA 4.0Updated 25 July 2025

Ridge Computers, Inc. was a U.S.-based computer manufacturer operating from 1980 until 1990, recognized for its early production of deskside workstations and workgroup servers, which later advanced into superminicomputers. The firm claimed to have introduced the first commercially available Reduced Instruction Set Computer (RISC) systems.

Company history

Established in May 1980 in Santa Clara, California by a group of six entrepreneurs—five originating from Hewlett-Packard and one from Zilog—the company’s name was inspired by Montebello Ridge, a favored cycling route for two of the founders.

By the end of 1981, Ridge had developed its initial prototype, which entered beta testing by early 1983 and was showcased at Comdex that fall. Initial processors employed bit-slice architectures constructed from "Fast" 7400-series integrated circuits alongside PAL components. Although Ridge’s CPU design sparked debate over its classification as RISC due to features such as variable-length instructions and microcoded control, it maintained its status as an early example of a RISC system.

Ridge competed with established industry leaders like Digital Equipment Corporation’s VAX-11 and emerging RISC companies including Celerity Computing and Pyramid Technology. Marketed as "personal mainframes," Ridge’s systems targeted professionals such as engineers and designers utilizing scientific computing, CAD, imaging, animation, and research software. A notable client, Pacific Data Images, transitioned from DEC VAX systems to Ridge 32s, resulting in a twofold increase in performance.

During the early 1980s, Ridge formed technology-sharing partnerships with Groupe Bull of France and Convergent Technologies to broaden its international presence. In September 1985, Robert J. Kunze from Hambrecht & Quist joined the company’s Board of Directors.

By the mid-1980s, Ridge faced financial difficulties; in early 1986 it secured $1 million towards a planned $10 million refinancing effort led by Hambrecht & Quist and Groupe Bull. Bob O. Evans of Hambrecht & Quist assumed the role of CEO. To enhance market penetration, Ridge introduced academic discount programs in both the United States and the United Kingdom.

In 1987, Ridge entered a joint marketing collaboration with Apollo Computer aimed at promoting hybrid systems that combined Apollo workstations with Ridge superminicomputers. Nonetheless, Ridge acknowledged the necessity of adopting Very Large Scale Integration (VLSI) technology to stay competitive; although experimental CPUs utilizing Fujitsu gate arrays were developed, no VLSI-based products were released commercially.

In early 1988, the company underwent restructuring that reduced its workforce by 45%, appointed Michael Preletz as CEO, and redirected its focus towards commercial sales amid delays in delivering the new CPU for the 5100 model. Ultimately, Ridge Computers ceased operations in April 1990.

Sales estimates indicate that Ridge directly sold between 400 and 600 units, with several hundred additional systems licensed to Bull—amounting to roughly 1,000 units overall. The architectural design of Ridge influenced other initiatives such as the Cerberus multiprocessor simulator’s CPU model.

People

At its height, Ridge employed approximately 150 staff members. Important founders and key personnel included:

Founders

Edward J. Basart, previously at Hewlett Packard working on the HP 3000 system, served as vice-president of software development at Ridge before co-founding Network Computing Devices (NCD).
Dave Folger, the sole founder from Zilog, initially headed software development and later became president and CEO until his departure in 1986.
Ron Kolb and Hugh Martin, both former HP employees, contributed significantly to hardware engineering. Martin eventually joined Apple to work on Project Aquarius.
John Sell, also an HP alumnus with experience on the HP 3000 Series, led hardware development efforts at Ridge before moving to Apple where he spearheaded PowerPC Macintosh architecture projects.
Neil C. Wilhelm joined from HP but exited after only a few months.

Additional Personnel

Sally Ahnger contributed to file system and distributed system development before transitioning to Sun Microsystems.
Judy Bruner served as Chief Financial Officer from 1984 to 1988, having previously worked at HP and subsequently moving to 3Com.
Bob Cook, an engineer and mechanical designer, was responsible for creating the Ridge 32S chassis.
Dave Cornelius, a Senior Software Engineer, departed to join NCD.
Dale Dell'Ario held roles as program manager, designer, and engineer.
Aprelle Deuell worked as a staff accountant between 1985 and 1988.
Mike Haden developed compiler integration for Green Hills and later joined Green Hills Software Inc.
Michael Harrigan functioned as product manager and was a co-founder of NCD.
Mehdi Jazayeri managed projects related to programming languages, focusing on enhancing compiler technologies.
Marjorie Kondo transitioned from company secretary to managing personnel and facilities.
Bruce K. Leisz was vice-president of manufacturing from 1983 until 1988.
Christopher B. Paisley held positions as Chief Financial Officer and Vice-president of Finance.
Chip Pessa directed CPU development efforts.
Nicholas D'Arcy Roche, who became president and COO in 1986, brought experience from IBM and Soft Switch.
Marilyn Miller Roche established the telemarketing division.
Michael Schulman, an application engineer, later joined SGI.
Bill Shellooe served as vice-president overseeing Marketing and Sales.
Michael Splain, part of the technical team responsible for diagnostic tools for Ridge’s single-chip CPU, later moved to Sun Microsystems.
Harry Taxin held the position of vice-president for Marketing & Sales.

Other notable contributors included Doug Klein, Dana Craig, and David Marlin Hanttula; Klein was also a co-founder of NCD.

Ridge Operating System (ROS)

The initial Ridge Computers platforms operated on the Ridge Operating System (ROS), a message-passing OS featuring virtual memory and cost-effective process management. Its microkernel design drew inspiration from Stanford University's V-system, aiming to create a distributed environment with comprehensive network transparency. The compact kernel—originally sized at 8 KB—handled memory management, interprocess communication, and interrupt processing, while server processes offered Unix-compatible interfaces alongside file system emulation. ROS integrated elements from both Unix System V and BSD.

Despite these capabilities, ROS encountered performance bottlenecks in multiuser scenarios and had difficulties managing Unix processes effectively. Recommendations emerged advocating for kernel-level file system support and updated message-passing mechanisms. Even the company founders eventually regarded ROS as a commercial disadvantage. By 1987, Ridge transitioned to Bull’s ported Unix variant, RX/V, which largely supplanted ROS across their systems.

Ridge 32

Introduced in the third quarter of 1982, the Ridge 32 featured the V1 CPU architecture nicknamed "Waterfall," segmented into integer processing, memory management, and floating-point units equipped with dedicated registers. Utilizing bit-slice technology, it supported instructions of 16-, 32-, and 48-bit lengths.

Ridge 32C

Launched in 1984, the Ridge 32C accommodated between one and four users.

Ridge 32S

Also released in 1984, the Ridge 32S was designed for single-user operation and incorporated the updated V2 CPU board set.

Ridge 32/1x0, 32/3x0, 32/5x0

In 1985, Ridge introduced the 32/1x0 and 32/3x0 series, which included models such as the 32/110, 32/130, 32/310, and 32/330. The following year, in 1986, the Ridge 32/530 was added to the lineup.

Ridge 32 Turbo RX

By the latter half of 1987, the Ridge 32 Turbo RX succeeded the earlier 32/1x0 and 32/3x0 models, replacing them in the product portfolio.

Server/RT

Launched in March 1986, the Server/RT was designed to serve hybrid network environments by delivering file and processing capabilities specifically for IBM PC workstations.

Ridge 3200

The Ridge 3200 series was unveiled in May 1986, offering support for up to 64 concurrent users. Notable models included the 3200/90 and 3200/95, both utilizing the Headwall CPU architecture.

Ridge 5100

Announced in September 1987 with anticipated availability in early 1988, the Ridge 5100 incorporated a novel VLSI-based CPU developed under Project Sunrise. Positioned as Ridge’s fourth-generation RISC platform, it targeted performance levels of approximately 14 MIPS and user capacity up to 128. Although funding was secured and architectural improvements—such as a larger register set and extended address space—were proposed, the Sunrise CPU failed to progress to production due to underwhelming early chip performance.

Groupe Bull

In April 1984, Groupe Bull established a strategic alliance with Ridge by obtaining manufacturing licenses for Ridge-based systems through its minicomputer branch Bull-SEMS at their Grenoble facility. These systems were marketed under the SPS 9 series brand. Bull also made a financial investment in Ridge and gained representation on its board. By October of that year, Bull had acquired an 11% ownership stake; SPS 9 units began shipping in December.

The initial SPS offerings comprised models like the SPS 9/40 and SPS 9/60 running ROS. Later expansions included SPS models such as the SPS 9/400, SPS 9/600, SPS 9/800, and SPS 9/830. Bull developed SPIX, a Unix System V derivative enhanced with BSD features tailored for Ridge architectures; this OS was sold on SPS hardware and as RX/V on Ridge-branded systems.

By September 1987, Bull’s shareholding had grown close to 20%. In early 1988, Bull rebranded its remaining SPS model as the DPX 5000. Concurrently, Bull’s research division initiated the Aurore CPU project aimed at creating next-generation processors compatible with Ridge systems but discontinued it in March 1987 after Ridge obtained funding for Sunrise. Difficulties adapting to Sunrise’s architectural revisions combined with concerns over Ridge’s partnerships led Bull to gradually disengage from the Ridge platform.

Software and applications

Significant software packages and specialized applications developed for or operating on Ridge and Bull-SEMS SPS 9 computers include:

Cericor Inc.’s CDA 5000 design automation system, offered for the Ridge models 32C and 32S starting in 1985.
A collaboration with Silicon Graphics resulting in integration of their Geometry Engine with the Ridge 32 platform in late 1984.
A customized variant of Network Innovations Corp.’s Multiplex product that enabled MS-DOS spreadsheet and database programs to access relational databases hosted on Ridge 3200 systems running RX/V.
The Ansys structural analysis software available on the Ridge 32 from September 1984 onward.
Proprietary graphics software such as Pacific Data Systems’ animation package and F. Sillion’s light interreflection calculation tool.
Support for the Eiffel object-oriented programming language on Bull SPS 9 machines running AT&T System V or BSD Unix following its commercial launch in late 1986.
Ecad Inc.’s Simon digital MOS circuit simulator version compatible with Ridge systems operating AT&T Unix released in January 1986.
The PODA graphical animation system designed for legged robots running on a Ridge 32C.
Porting of the EQ3/6 Geochemical Modelling Plan from CDC and Cray supercomputers to dedicated Ridge machines enabled by full FORTRAN 77 compatibility.
Replacement of a Xerox SIGMA9 mainframe by a Ridge 32C at Oberlin Conservatory’s TIMARA program supporting electronic music research through specialized audio interfaces.
Ports of Lisp and Mainsail programming languages adapted for use on the SPS 9 platform.

These software solutions broadened the capabilities of Ridge and Bull-SEMS SPS 9 systems across engineering, scientific analysis, computer graphics, and music technology sectors, reinforcing their position within the Unix workstation market.

External links

RISC – Episode of The Computer Chronicles, PBS KCSM, dated 7 October 1986
Seok, Tae Yoon (December 1986). Performance Assessment of a Ridge 32 Computer System. MSc thesis, Florida Atlantic University. [1]
Collection of Ridge Documents hosted at bitsavers.org