Data General Nova
The Nova is a series of 16-bit minicomputers released by the American company Data General. The Nova family was very popular in the 1970s and ultimately sold tens of thousands of units.
The first model, known simply as "Nova", was released in 1969. The Nova was packaged into a single 3U rack-mount case and had enough computing power to handle most simple tasks. The Nova became popular in science laboratories around the world. It was followed the next year by the SuperNOVA, which ran roughly four times as fast, making it the fastest mini for several years.
Introduced during a period of rapid progress in integrated circuit design, the line went through several upgrades over the next five years, introducing the 800 and 1200, the Nova 2, Nova 3, and ultimately the Nova 4. A single-chip implementation was also introduced as the microNOVA in 1977, but did not see widespread use as the market moved to new microprocessor designs. Fairchild Semiconductor also introduced a microprocessor version of the Nova in 1977, the Fairchild 9440, but it also saw limited use in the market.
The Nova line was succeeded by the Data General Eclipse, which was similar in most ways but added virtual memory support and other features required by modern operating systems. A 32-bit upgrade of the Eclipse resulted in the Eclipse MV series of the 1980s.
History
Edson de Castro and the PDP-X
was the Product Manager of the pioneering Digital Equipment Corporation PDP-8, a 12-bit computer widely referred to as the first true minicomputer. He also led the design of the upgraded PDP-8/I, which used early integrated circuits in place of individual transistors.During the PDP-8/I process, de Castro had been visiting circuit board manufacturers who were making rapid advances in the complexity of the boards they could assemble. de Castro concluded that the 8/I could be produced using fully automated assembly on large boards, which would have been impossible only a year earlier. Others within DEC had become used to the smaller boards used in earlier machines and were concerned about tracking down problems when there were many components on a single board. For the 8/I, the decision was made to stay with small boards, using the new "flip-chip" packaging for a modest improvement in density.
During the period when the PDP-8 was being developed, the introduction of ASCII and its major update in 1967 led to a new generation of designs with word lengths that were multiples of 8 bits rather than multiples of 6 bits as in most previous designs. This led to mid-range designs working at 16-bit word lengths instead of DEC's current 12- and 18-bit lineups. de Castro was convinced that it was possible to improve upon the PDP-8 by building a 16-bit minicomputer CPU on a single 15-inch square board.
In 1967, de Castro began a new design effort known as "PDP-X" which included several advanced features. Among these was a single underlying design that could be used to build 8-, 16-, and 32-bit platforms. This progressed to the point of producing several detailed architecture documents. Ken Olsen was not supportive of this project, feeling it did not offer sufficient advantages over the 12-bit PDP-8 and the 18-bit PDP-9. It was eventually canceled in the spring of 1968.
Design
Cancelation of the PDP-X prompted de Castro to consider leaving DEC to build a system on his own. He was not alone; in late 1967 a group of like-minded engineers formed to consider such a machine. The group included Pat Green, a divisional manager; Richard Sogge, another hardware engineer; and Henry Burkhardt III, a software engineer. In contrast to the PDP-X, the new effort focused on a single machine that could be brought to market quickly, as de Castro felt the PDP-X concept was far too ambitious for a small startup company.Discussing it with the others at DEC, the initial concept led to an 8-bit machine which would be less costly to implement. The group began talking with Herbert Richman, a salesman for Fairchild Semiconductor who knew the others through his contacts with DEC. At the time, Fairchild was battling with Texas Instruments and Signetics in the rapidly growing TTL market and were introducing new fabs that allowed more complex designs. Fairchild's latest 9300 series allowed up to 96 gates per chip, and they had used this to implement a number of 4-bit chips like binary counters and shift registers.
Using these ICs reduced the total IC count needed to implement a complete arithmetic logic unit, the core mathematical component of a CPU, allowing the expansion from an 8-bit design to 16-bit. This did require the expansion of the CPU from a single printed circuit board to two, but such a design would still be significantly cheaper to produce than the PDP-8/I while still being more powerful and ASCII-based. A third board held the input/output circuitry and a complete system typically included another board with 4 kB of random-access memory. A complete four-card system fit in a single rackmount chassis.
The boards were designed so they could be connected together using a printed circuit backplane, with minimal manual wiring, allowing all the boards to be built in an automated fashion. This greatly reduced costs over the PDP-8/I, which consisted of many smaller boards that had to be wired together at the backplane, which was itself connected together using wire wrap. The larger-board construction also made the Nova more reliable, which made it especially attractive for industrial or lab settings.
The new design used a simple load–store architecture which would reemerge in the RISC designs in the 1980s. Because the complexity of a flip-flop was being rapidly reduced as they were implemented in chips, the design offset the lack of addressing modes of the load–store design by adding four general-purpose accumulators, instead of the single register that would be found in similar low-cost offerings like the PDP series.
Introduction
Late in 1967, Richman introduced the group to New York-based lawyer Fred Adler, who began canvassing various funding sources for seed capital. By 1968, Adler had arranged a major funding deal with a consortium of venture capital funds from the Boston area, who agreed to provide an initial investment with a second available for production ramp-up. de Castro, Burkhart and Sogge quit DEC and started Data General on 15 April 1968. Green did not join them, considering the venture too risky, and Richman did not join until the product was up and running later in the year.Work on the first system took about nine months, and the first sales efforts started that November. They had a bit of luck because the Fall Joint Computer Conference had been delayed until December that year, so they were able to bring a working unit to San Francisco where they ran a version of Spacewar!. DG officially released the Nova in 1969 at a base price of, advertising it as "the best small computer in the world." The basic model was not very useful out of the box, and adding RAM in the form of core memory typically brought the price up to. In contrast, a PDP-8/I with was priced at.
The first sale was to a university in Texas, with the team hand-building an example which shipped out in February. However, this was in the midst of a strike in the airline industry and the machine never arrived. They sent a second example, which arrived promptly as the strike had ended by that point, and in May the original one was finally delivered as well.
The system was successful from the start, with the 100th being sold after six months, and the 500th after 15 months. Sales accelerated as newer versions were introduced, and by 1975 the company had annual sales of.
SuperNOVA
Ken Olsen had publicly predicted that DG would fail, but with the release of the Nova it was clear that was not going to happen. By this time, a number of other companies were talking about introducing 16-bit designs as well. Olsen decided these presented a threat to their 18-bit line as well as 12-bit, and began a new 16-bit design effort. This emerged in 1970 as the PDP-11, a much more complex design that was as different from the PDP-X as the Nova was. The two designs competed heavily in the market.Rumors of the new system from DEC reached DG shortly after the Nova began shipping. In spring 1970 they hired a new designer, Larry Seligman, to leapfrog any possible machine in the making. Two major changes had taken place since the Nova was designed; one was that Signetics had introduced the 8260, a 4-bit IC that combined an adder, XNOR and AND, meaning the number of chips needed to implement the basic logic was reduced by about three times. Another was that Intel was aggressively talking up semiconductor-based memories, promising 1024 bits on a single chip and running at much higher speeds than core memory.
Seligman's new design took advantage of both of these improvements. To start, the new ICs allowed the ALU to be expanded to full 16-bit width on the same two cards, allowing it to carry out math and logic operations in a single cycle and thereby making the new design four times as fast as the original. In addition, new smaller core memory was used that improved the cycle time from the original's 1,200 ns to 800 ns, offering a further improvement. Performance could be further improved by replacing the core with read-only memory; lacking core's read–write cycle, this could be accessed in 300 ns for a dramatic performance boost.
The resulting machine, known as the SuperNOVA, was released in 1970. Although the initial models still used core, the entire design was based on the premise that faster semiconductor memories would become available and the platform could make full use of them. This was introduced later the same year as the SuperNOVA SC, featuring semiconductor memory. The much higher performance memory allowed the CPU, which was synchronous with memory, to be further increased in speed to run at a 300 ns cycle time. This made it the fastest available minicomputer for many years. Initially the new memory was also very expensive and ran hot, so it was not widely used.