Amdahl Corporation

Amdahl Corporation
Company type	Subsidiary (after 1997)
Industry	Computer systems
Founded	1970
Founder	Gene Amdahl
Fate	Became wholly owned subsidiary of Fujitsu in 1997
Headquarters	Sunnyvale, California, United States
Key people	Gene Amdahl (founder), Jack Lewis (CEO)
Products	IBM mainframe-compatible computer systems, UNIX and open system software, servers, storage subsystems, data communication devices, application development tools, training and consulting services
Parent	Fujitsu (from 1997)

Amdahl Corporation was a technology firm that specialized in manufacturing computer systems compatible with IBM mainframes, including some models recognized as supercomputers rivaling those from Cray Research. Established in 1970 by Gene Amdahl, an ex-IBM engineer and the chief designer of the System/360, it became a wholly owned subsidiary of Fujitsu in 1997. The company’s headquarters were located in Sunnyvale, California.

Starting with its initial system released in 1975, Amdahl’s strategy centered on delivering mainframe computers that could directly replace IBM mainframes while offering superior reliability, enhanced speed, and reduced expenses. Their machines were notable for being more compact, consuming less power, and using air cooling instead of chilled water systems. This favorable balance of cost and performance allowed Amdahl to emerge as one of the few significant challengers to IBM within the lucrative mainframe sector, achieving approximately 8% of the worldwide market and dominating markets such as the Carolinas. The brand earned a strong reputation among IBM clientele due to its competitive advantages.

During the late 1980s, as the mainframe landscape transformed, Amdahl expanded its offerings to encompass UNIX and open system software solutions, along with servers, storage subsystems, data communication devices, application development tools, and also provided training and consulting services.

ACS

Beginning in 1965, Gene Amdahl was employed at IBM working on the ambitious IBM Advanced Computer Systems project (ACS), which aimed to create the fastest computer globally. In early 1968, he recommended abandoning the ACS-1 design in favor of one compatible with the System/360, a proposal that succeeded in a management competition. Following this shift, many ACS executives departed, and Amdahl took charge of developing the new system concept.

In July 1969, IBM declared that older software would be released into the public domain, while new software would be sold separately. This policy change responded to antitrust pressures from third-party vendors like Applied Data Research. By separating software sales from hardware, IBM opened the door for machines compatible with its systems since restricting software exclusively to IBM hardware would have violated antitrust regulations.

In May 1969, Amdahl suggested producing three machines based on ACS concepts following IBM’s tiered pricing model where performance levels were priced roughly twice as high per tier. To make the highest-end machine affordable, prices for lower-tier models needed to decrease below existing levels. Management rejected these proposals, effectively halting ACS development. Subsequently, Amdahl departed IBM early in 1970 with intentions to create compatible computer systems independently.

Forming Amdahl

Collaborating with former ACS engineers, Amdahl shifted focus from building the fastest possible computer to designing systems using standardized five-by-five component cards. Although these were less powerful than ACS designs, they were simpler and more cost-effective to manufacture. The design process utilized automated circuit board layout software operated on IBM 1130 machines. Initially seeking partners for circuit production, they engaged with Motorola, but disagreements over software sharing led them to partner with Advanced Memory Systems instead.

Raising capital proved difficult due to widespread doubts about competing against IBM; earlier attempts by companies such as RCA and Xerox had failed despite significant funding. Leveraging his relationship with Fujitsu, Amdahl secured a $5 million investment following extensive technical negotiations. This investment encouraged matching $5 million contributions from Nixdorf and an additional $5 million from Fujitsu to preserve their influence within the company. Amdahl Corporation was officially established in 1971.

470 series

During this era, IBM unveiled the System/370 lineup, which offered enhanced speed and lower costs compared to the System/360. Amdahl sought to provide a more affordable alternative targeting IBM’s premium 370 models, intending to challenge IBM's pricing approach. This initiative resulted in the creation of the 470/6 series.

Partnering with Fujitsu, Amdahl developed distinctive air-cooled processors utilizing advanced emitter-coupled logic (ECL) technology. These processors incorporated patented finned heat sinks that allowed complete air cooling—contrasting with IBM’s water-cooled designs—thereby cutting both installation and upkeep expenses.

The system architecture progressed from a five-by-five to a six-by-seven multi-layer card configuration, arranged vertically without employing a traditional backplane. Cooling was achieved through robust "Tarzan" fans positioned in each column. Each unit included a Nova 1200 computer to manage the CRT console and channel command tasks compatible with IBM’s 370/165 and 370/168 models.

Initially missing virtual memory capabilities, Amdahl revised its design following IBM’s introduction of "dynamic address translation," leading to the 470V/6 variant in 1974. This model operated at twice the speed of the IBM 370/168 for similar costs, occupied only one-third of the floor area, and eliminated the need for water cooling systems.

The inaugural 470V/6 was installed at NASA Goddard Space Flight Center in June 1975, completed within five days—significantly quicker than typical IBM installations. Subsequent deployments included the University of Michigan, Texas A&M, and Computer Usage Corporation. By August 1977, after reaching 55 installed systems, Amdahl increased production from four to six units per month.

For more than twenty years, Amdahl maintained intense competition with IBM in the high-end mainframe sector, capturing up to a 24% share of the market. This success was partly due to antitrust agreements that guaranteed customers reasonable licensing terms for IBM mainframe software. Amdahl’s machines supported all peripherals from both the 360 and 370 series, and although initially opposed, IBM eventually provided maintenance services for these mixed environments as Amdahl grew profitable in hardware support.

Later 470s

In February 1977, Amdahl introduced the 470V/6-II, which offered performance gains of 5 to 15 percent at a modestly higher price point. The next month saw the launch of the smaller 470V/5 model, delivering between 60 and 70 percent of the /6-II’s performance with an upgrade option priced at $780,000. Shipments began in September 1977. Simultaneously, the 470V/7 was announced to rival IBM’s 3033 system; it incorporated updated circuitry along with innovations from the ACS project, with initial deliveries commencing in August 1978.

The 470V/8 arrived in 1980 featuring a high-speed 64 KB cache and groundbreaking hardware virtualization known as the "Multiple Domain Facility." Additionally, Amdahl rolled out a '470 accelerator' variable-speed capability on the /5 and /7 models, allowing clients to boost performance temporarily and pay according to usage hours. This pricing strategy became popular by combining scalable computing power with cost management.

580 series

During the late 1970s, Amdahl initiated the 580 project with the goal of creating next-generation system architectures. Although engineering teams and Fujitsu supported multiprocessor configurations, company founder Gene Amdahl preferred focusing on a faster single-processor design and departed in 1979 to establish Trilogy Systems. After his exit and with Fujitsu’s growing influence, Amdahl entered the large-scale multiprocessor arena in the mid-1980s, releasing models such as the 5860, 5870 (designed as an attached processor), and the fully multiprocessor-capable 5880.

The architecture of the 580 series incorporated chips mounted on Multi-Chip Carriers (MCCs), arranged in an 11-by-11 grid within cooling frames optimized for high airflow. These processor "side panels" were engineered to maintain synchronous operation at elevated clock speeds (with cycle times between 15 and 18 nanoseconds), supported by sophisticated cooling mechanisms.

From a strategic standpoint, Amdahl aimed to enhance its competitive position by merging with a leading enterprise storage company to complement its mainframe product line. After an unsuccessful merger attempt with Memorex in 1979, discussions advanced toward a merger with Storage Technology Corporation (STC). However, Fujitsu—then a significant shareholder—opposed this alliance, causing it to fall through. STC’s later failed attempt to enter the mainframe market resulted in bankruptcy by 1984. Around this time, Amdahl permitted Fujitsu to acquire nearly half of its shares, eventually leading to full ownership years later.

Throughout the 1980s, Amdahl diversified into IBM-compatible peripheral devices, launching successful products such as the 4705 communications controller in 1980 and the 6000 direct-access storage unit in 1982. Under CEO Jack Lewis’s guidance, these offerings contributed significantly to revenue growth. Nevertheless, dependence on mainframe-centric hardware constrained expansion as market preferences shifted toward x86 processors. Anticipating this evolution, Amdahl increased its emphasis on software solutions and consulting services to broaden its business portfolio.

Market exit

In 1987, Amdahl discontinued its Aspen initiative—an effort to develop a proprietary operating system—and redirected focus toward its Unix-based Amdahl UTS platform.

By the early 1990s, weakening mainframe sales led to substantial quarterly financial losses. In response, management implemented workforce reductions totaling approximately 3,800 employees between 1992 and 1993 and halted hardware development projects in favor of reselling Sun Microsystems systems.

Amdahl briefly capitalized during IBM's transition from bipolar to CMOS technology in the early to mid-1990s. Initial IBM CMOS processors lagged behind their bipolar predecessors in performance, providing Amdahl with a temporary competitive advantage. However, IBM’s CMOS strategy ultimately enabled faster and more cost-effective mainframes. By the year 2000, IBM’s 64-bit zSeries 900 outperformed Amdahl’s 31-bit Millennium and OmniFlex servers. Fujitsu/Amdahl declared no intention to invest over $1 billion required for developing a competitive 64-bit platform.

Amdahl’s ObjectStar software failed to achieve market success and was eventually sold through a management buyout before being acquired by TIBCO in 2005.

Amdahl customer options

IBM's z/OS version 1.5 marked the final release supporting 31-bit mainframes like those produced by Amdahl; official support ceased in 2007. Subsequent IBM operating systems—including z/VSE Version 4 (2006) and z/TPF (2005)—require exclusively 64-bit hardware platforms, effectively ending support for 31-bit architectures. Some Amdahl machines remained operational until mid-2006, with Fujitsu/Amdahl providing support services until March 2009.

The introduction of IBM’s zSeries 890 in 2004 and later systems such as the z9 BC (2006) and System z10 BC (2008) offered viable upgrade paths for former Amdahl users, driving down prices for secondhand equipment. Currently, Fujitsu/Amdahl markets used IBM mainframes and offers migration assistance to facilitate transitions within IBM-compatible environments. The IBM z13 represented the last server supporting ESA/390 architecture; newer models exclusively accommodate 64-bit operating systems. Alternatives for legacy applications include unsupported operation, rewriting software, or employing emulation technologies like FLEX-ES—a mainframe instruction set emulator supporting ESA/390 and certain z/Architecture programs.

Amdahl’s efforts in ESA/390 emulation evolved into Platform Solutions Inc. (PSI), which received backing from Intel, HP, Microsoft, and others. PSI developed Itanium-based systems capable of emulating z/Architecture hardware to run IBM operating systems alongside Linux and UNIX variants within LPAR environments. PSI began shipping products in early 2007 but soon faced patent infringement lawsuits from IBM concerning licensing issues. PSI responded with antitrust allegations against IBM. In July 2008, IBM acquired PSI, terminating all legal disputes; PSI’s product lines have since been discontinued.

Fujitsu GS21

Fujitsu continues to offer its "GlobalServer" (GS21) mainframe series exclusively within the Japanese market. These GS21 models operate on ESA/390 (31-bit) instruction sets derived from Amdahl technology but support only Fujitsu’s proprietary operating systems: OSIV/MSP-EX and OSIV/XSP. The MSP operating system bears similarity to IBM’s MVS/ESA, whereas XSP is comparable to IBM’s VSE/ESA. In terms of instruction set compatibility, the GS21 hardware corresponds with IBM System/390 G5 and G6 mainframes from the late 1990s. Fujitsu has no intention of transitioning to the 64-bit z/Architecture.

The company has announced plans to phase out the GS21 lineup by 2030, with full support concluding in 2035, to encourage clients toward modernization initiatives.

Sources

External links

Amdahl 470V/6 Machine Reference, 50 pages, 1975, PDF/A, 7.8MB.
Amdahl 470V/6-II Machine Reference Manual, 50 pages, March 1978, PDF/A, 9.4MB.
Amdahl 470V/8 Computing System Machine Reference Manual, April 1981, PDF/A, 3.8MB.
Various Amdahl publications available as PDFs from Bitsavers.org.
Amdahl 470V/6, P2 is archived at the Computer History Museum, catalog X436.84A.
Photographs of an Amdahl 470V/6 at the Computer History Museum.
Photographs of an Amdahl 470V/6 at the University of Michigan.
Photographs of an Amdahl 5860 at the University of Newcastle.
Oral history interview with Gene Amdahl at the Charles Babbage Institute, University of Minnesota.
Fujitsu GS21 – System/390 Compatible Servers, formerly Amdahl.
Fujitsu GS servers MSP and XSP roadmap

ACS