FormalPara Key Topics

DEC

Minicomputers

PDP-11

VAX-11/780

Amdahl 470

IBM System/370

9.1 Introduction

The minicomputer was a new class of low-cost computers that arose during the 1960s. The development of minicomputers was facilitated by the introduction of integrated circuits, and their improved performance and declining cost. Minicomputers were distinguished from the large mainframe computers by price and size, and they formed a class of the smallest general-purpose computers.

Mainframes were large expensive machines (typically costing over $1 million), and they required separate rooms for technicians and operation, whereas minicomputers cost well under $100,000, and they were designed for direct, personal interaction with the programmer.

Digital Equipment Corporation (DEC) and Control Data Corporation (CDC) introduced small or minicomputers in the early 1960s. These included DEC’s PDP-1, which was released in 1961, and the CDC-160A, which was released in 1960. These machines cost $110,000 and $60,000, respectively, which was a fraction of the cost of a mainframe computer.

The DEC PDP series of minicomputers became popular in the 1960s. The PDP-8 minicomputer was released in 1965, and it was a 12-bit machine with a small instruction set. The PDP-11 was a highly successful series of 16-bit minicomputers, and it remained a popular product for over 20 years from its release in 1970 to the early 1990s.

Gene Amdahl was the chief architect for the IBM System/360, and he resigned from IBM to set up Amdahl Corporation in 1970. His goals were to develop a mainframe that would provide better performance than the existing IBM machines and do so a lower cost, as well as being compatible with IBM hardware and software.

Amdahl Corporation launched its first product, the Amdahl 470V/6, in 1975. This was an IBM S/370 compatible mainframe that could run IBM software, and so it was an alternative to a full IBM proprietary solution. It meant that companies around the world now had the choice of continuing to run their software on IBM machines or purchasing the cheaper and more powerful IBM compatibles produced by Amdahl. Amdahl Corporation became a major competitor to IBM in large-scale computer placements.

Amdahl Corporation’s success led to a price war with IBM, with the latter offering discounts to its customers to protect its market share.

9.2 DEC’s Minicomputers

Ken Olsen and Harlan Anderson founded Digital Equipment Corporation (DEC) in 1957. It was a spin off from MIT’s Lincoln computer laboratory, and it was an innovative and forward-thinking company. It became the second largest computer company in the world in the late 1980s, with revenues of over $14 billion and over 100,000 employees. It dominated the minicomputer era from the 1960s to the 1980s, with its PDP and VAX series of computers, which were very popular with the engineering and scientific communities.

DEC’s first computer, the “Programmed Data Processor” (PDP-1), was released in 1961 (Fig. 9.1). This 18-bit machine was a relatively inexpensive computer for the time, and it cost $110,000. The existing IBM mainframes were substantially more expensive, and so DEC’s minicomputers were relatively affordable to businesses. It was a simple and reasonably easy to use computer with 4000 words of memory.

Fig 9.1
figure 1

The PDP-1 computer

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The PDP series of minicomputers were elegant and reasonably priced and dominated the new minicomputer market segment. They were an alternative to the multimillion dollar mainframe computers offered by IBM to large corporate customers. Research laboratories, engineering companies, and other organizations with large computing needs all used DEC’s minicomputers.

The PDP-8 minicomputer (Fig. 7.3) was released in 1965, and it was a 12-bit machine with a small instruction set. It was a major commercial success for DEC with many sold to schools and universities. The PDP-11 was a highly successful series of 16-bit minicomputer, and it remained a popular product for over 20 years from the 1970s to the 1990s.

Gordon Bell was one of the earliest employees of the company, and he played an important role in the development of the PDP family of minicomputers. He designed the multiplier/divider unit and the interrupt system for the PDP-1 computer, which built upon work done at the MIT Lincoln Laboratory. He later became vice president of research and development at DEC, and he was the architect of several PDP computers. He later led the development of the 32-bit VAX series of computers, and he was involved in the design of around 30 microprocessors.

The VAX series of minicomputers were derived from the best-selling PDP-11, and the VAX was the first widely used 32-bit minicomputer. The VAX-11/780 was released in 1978, and it was a major success for the company. The VAX product line was a competitor to the IBM System/370 series of mainframe computers. The VAX minicomputers used the Virtual Memory System (VMS) operating system.

The rise of the microprocessor and microcomputer led to the availability of low cost personal computers, and this later challenged DEC’s product line. DEC was slow in recognizing the importance of these developments, and Olsen’s statement from the mid-1970s “There is no need for any individual to have a computer in his home” suggests that DEC were totally unprepared for the revolution in home and personal computing and its threat to DEC’s business. DEC was too late in responding to the paradigm shift in the industry, and this proved to be fatal. Compaq acquired DEC in 1998 for $9.8 billion, and HP later acquired Compaq.

9.2.1 PDP-11

The PDP-11 (Fig. 9.2) was a family of 16-bit minicomputers produced by DEC from 1970 up to the early 1990s. It was designed by Harold McFarland, with the prototype ready in 1969, and the PDP-11 released in 1970. There were several models in the PDP-11 family.

Fig. 9.2
figure 2

PDP-11

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It was one of DEC’s most successful computers, with over 600,000 machines sold. It was the only 16-bit computer made by the company, as its successor was the 32-bit VAX:11 series. It started its life as a minicomputer and ended its life as micro/super-microcomputer. The release price of the PDP-11 in 1970 was a very affordable $20,000.

Its central processing unit had eight 16-bit registers, six general-purpose registers, the stack pointer, and a program counter. It included software such as an editor, debugger, and utilities. The size of its memory was 128 KB.

The PDP-11 was very useful for multiuser and multitask applications, and one of the earliest versions of the UNIX operating system ran on a PDP-11/20 in 1973 (the first version was written in assembly language and ran on a PDP-7). The VAX line at Digital began as an enhancement to the PDP-11 architecture.

9.2.2 The VAX 11/780

The Virtual Address eXtension (VAX) was a family of minicomputers produced by DEC from the mid-1970s up to the late 1980s. This family used processors implementing the VAX instruction set architecture, and its members included minicomputers such as the VAX-11/780, /782, /784, /785, /787, /788, /750, /725, and /730. The VAX product line was a competitor to the IBM System/370 series of computers.

The VAX series was derived from the PDP-11 minicomputer and the VAX-11/780 (Fig. 9.3) was the first member of the family. It was the first widely used 32-bit minicomputer, and it was released in 1978. It was the first one MIPS (Million Instructions per Second) machine, and it was a major success for the company.

Fig. 9.3
figure 3

VAX-11/780

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Several programming languages including Fortran-77, BASIC, COBOL, and Pascal were available for the machine. The VAX-11/780 used the DEC VMS operating system, which was a multiuser, multitasking, and virtual memory operating system. The VAX-11/780 remained the base system that every computer benchmarked its speed against for many years.

It supported 128KB to 8MB of memory through one or two memory controllers, and the memory was protected with error correcting codes. Each memory controller could support 128KB to 4MB of memory. For more detailed information on DEC, see [Sch:04].

9.3 The War Between IBM and Amdahl

Gene Amdahl (Fig. 8.2) resigned from IBM to set up Amdahl Corporation in 1970, and his goals were to develop a mainframe that would be compatible with the IBM System/360. Further, he intended that it would provide a superior performance at a lower cost than the existing IBM machine. Amdahl revised his plans to launch an IBM compatible System/370 mainframe following IBM’s introduction of its IBM System/370 mainframe.

Amdahl Corporation launched its first product, the Amdahl 470V/6, in 1975. This was an IBM System/370 compatible mainframe that could run IBM software, and so it was an alternative to a full IBM proprietary solution. It meant that companies around the world now had the choice of continuing to run their software on IBM machines or purchasing the cheaper and more powerful IBM compatibles produced by Amdahl.

Amdahl’s first customer was the NASA Goddard Institute for Space Studies, which was based in New York. The Institute needed a powerful computer to track data from its Nimbus weather satellite, and it had a choice between a well-established company such as IBM and an unknown company such as Amdahl. It seemed likely that IBM would be the chosen supplier. However, the institute was highly impressed with the performance of the Amdahl 470 V/6, and its cost was significantly less than the IBM machine.

The Amdahl 470 competed directly against the IBM System 370 family of mainframes. It was compatible with IBM hardware and software but cheaper than the IBM product: that is, the Amdahl machines provided better performance for less money. Further, the machine was much smaller than the IBM machine due to the use of large-scale integration (LSI) with many integrated circuits on each chip. This meant that the Amdahl 470 was one-third of the size of IBM’s 370. It was over twice as fast and sold for about 10% less than the IBM 370.

IBM’s machines were water-cooled, while Amdahl’s were air-cooled, which decreased installation costs significantly. Machine sales were slow initially due to concerns over Amdahl Corporation’s long-term survival, and the risks of dealing with a new player. IBM had a long established reputation as the leader in the computer field. The University of Michigan was Amdahl’s second customer, and it used the 470 in its education center. Texas A&M was Amdahl’s third customer, and they used the 470 for educational and administrative purposes. Amdahl Corporation was well on its way to success, and by 1977 it had over fifty 470 V/6 machines installed at various customer sites.

IBM launched a new product, the IBM 3033, in 1977 to compete with the Amdahl 470. However, Amdahl Corporation responded with a new machine, the 470 V/7, which was one and a half times faster than the 3033, and only slightly more expensive. Customers voted with their feet and chose Amdahl as their supplier, and by late 1978, it had sold over a hundred of the 470 V/7 machines.

IBM introduced a medium-sized computer, the 4300 series, in early 1979, and in late 1980, it announced plans for the 3081 processor which would have twice the performance of the existing 3033 on its completion in late 1981. In response, Amdahl announced the 580 series (Fig. 9.4), which would have twice the performance of the existing 470 series. The 580 series was released in mid-1982, but their early processors had some reliability problems and lacked some of the features of the new IBM product.

Fig. 9.4
figure 4

Amdahl 5860. (Courtesy of Robert Broughton, University of Newcastle)

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Amdahl moved into large system multiprocessor design from the mid-1980s. It introduced its 5890 model in late 1985, and its superior performance allowed Amdahl to gain market share and increase its sales to approximately $1 billion in 1986. It now had over 1300 customers in around 20 countries around the world. It launched a new product line, the 5990 processor, in 1988, and this processor outperformed IBM by 50%. Customers voted with their feet and chose Amdahl as their supplier.

It was clear that Amdahl was now a major threat to IBM in the high-end mainframe market. Amdahl had a 24% market share and annual revenues of $2 billion at the end of 1988. This led to a price war with IBM, with the latter offering discounts to its customers to protect its market share. Amdahl responded with its own discounts, and this led to a reduction in profitability for the company.

The IBM personal computer was introduced in the early 1980s, and by the early 1990s, it was clear that the major threat to Amdahl was the declining mainframe market. Revenue and profitability fell, and Amdahl shut factory lines and cut staff numbers. By the late 1990s, Amdahl was making major losses, and there were concerns about the future viability of the company.

It was clear by 2001 that Amdahl could no longer effectively compete against IBM following IBM’s introduction of its 64-bit zSeries architecture. Amdahl had invested a significant amount in research on a 64-bit architecture to compete against the zSeries, but the company estimated that it would take a further $1 billion and two more years to create an IBM-compatible 64-bit system. Further, it would be several years before they would gain any benefit from this investment as there were declining sales in the mainframe market due to the popularity of personal computers.

By late 2001, the sales of mainframes accounted for just 10% of Amdahl’s revenue, with the company gaining significant revenue from the sale of Sun servers. Amdahl became a wholly owned subsidiary of Fujitsu in 1997, and it exited the mainframe business in 2002. Today, it focuses on the server and storage side, as well as on services and consulting.

For more detailed information on Gene Amdahl, Amdahl Corporation, IBM, and Digital Equipment Corporation, see [ORg:13, ORg:15].

9.4 Review Questions

  1. 1.

    What is a minicomputer?

  2. 2.

    What factors led to the introduction of the minicomputer?

  3. 3.

    Describe the achievements of Gene Amdahl.

  4. 4.

    Describe the competition between Amdahl Corporation and IBM in the mainframe market.

  5. 5.

    What factors led to the demise of DEC and Amdahl?

  6. 6.

    What could DEC and Amdahl done differently?

  7. 7.

    Describe the achievements of Gordon Bell.

9.5 Summary

The minicomputer was a new class of low-cost computers that arose during the 1960s. The development of minicomputers was facilitated by the introduction of integrated circuits, as this helped to reduce cost and size of computers. Minicomputers were distinguished from the large mainframe computers by price and size, and they formed a class of the smallest general-purpose computers.

DEC introduced minicomputers from the early 1960s and the PDP-11 was a highly successful series of 16-bit minicomputers, and remained popular from the 1970s to the 1990s. The VAX series of minicomputers were derived from the PDP-11, and it was the first widely used 32-bit minicomputer.

The rise of the microprocessor and microcomputer led to the availability of low-cost home and personal computers, and this paradigm shift later challenged the mainframe and minicomputer market. DEC was too late in responding to the paradigm shift in the industry.

Gene Amdahl set up Amdahl Corporation in 1970, and his goals were to develop a mainframe that would be compatible with the IBM System/360. Amdahl’s mainframes were compatible with IBM computers but delivered superior performance, and this gave companies the choice of continuing to run their software on IBM machines or purchasing the cheaper and more powerful IBM compatibles produced by Amdahl.

Amdahl became a major threat to IBM in the high-end mainframe market, as customers placed orders with Amdahl at IBM’s expense. However, as the mainframe market declined in the 1990s, Amdahl failed to adapt to the rise of the personal computer, and it went through major financial difficulties and it was taken over by Fujitsu.