The CDC 8600 was the last of

Seymour Cray Seymour Roger Cray (September 28, 1925 – October 5, 1996)
– was an American

supercomputer A supercomputer is a type of computer with a high level of performance as compared to a general-purpose computer. The performance of a supercomputer is commonly measured in floating-point operations per second (FLOPS) instead of million instruc ...

designs while he worked for

Control Data Corporation Control Data Corporation (CDC) was a mainframe and supercomputer company that in the 1960s was one of the nine major U.S. computer companies, which group included IBM, the Burroughs Corporation, and the Digital Equipment Corporation (DEC), the N ...

. As the natural successor to the

CDC 6600 The CDC 6600 was the flagship of the 6000 series of mainframe computer systems manufactured by Control Data Corporation. Generally considered to be the first successful supercomputer, it outperformed the industry's prior recordholder, the I ...

and

CDC 7600 The CDC 7600 was designed by Seymour Cray to be the successor to the CDC 6600, extending Control Data Corporation, Control Data's dominance of the supercomputer field into the 1970s. The 7600 ran at 36.4 MHz (27.5 ns clock cycle) and had ...

, the 8600 was intended to be about 10 times as fast as the 7600, already the fastest computer on the market. The design was essentially four 7600's, packed into a very small chassis so they could run at higher clock speeds. Development started in 1968, shortly after the release of the 7600, but the project soon started to bog down. The dense packaging of the system led to serious reliability problems and difficulty cooling the individual components. By 1971, CDC was having

cash-flow Cash flow, in general, refers to payments made into or out of a business, project, or financial product. It can also refer more specifically to a real or virtual movement of money. *Cash flow, in its narrow sense, is a payment (in a currency), es ...

problems and the design was still not coming together, prompting Cray to leave the company in 1972. The 8600 design effort was eventually canceled in 1974, and Control Data moved on to the

CDC STAR-100 The CDC STAR-100 is a vector supercomputer that was designed, manufactured, and marketed by Control Data Corporation (CDC). It was one of the first machines to use a vector processor to improve performance on appropriate scientific applications. I ...

series instead. Cray revisited the 8600's basic design in his

Cray-2 The Cray-2 is a supercomputer with four vector processors made by Cray Research starting in 1985. At 1.9 GFLOPS peak performance, it was the fastest machine in the world when it was released, replacing the Cray X-MP in that spot. It was, ...

of the early 1980s. The introduction of

integrated circuit An integrated circuit (IC), also known as a microchip or simply chip, is a set of electronic circuits, consisting of various electronic components (such as transistors, resistors, and capacitors) and their interconnections. These components a ...

s solved the problems with dense packaging and liquid cooling addressed the heat issues. The Cray-2 is very similar to the 8600 both physically and conceptually.

Design

In the 1960s, computer design was based on mounting electronic components (

transistor A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch electrical signals and electric power, power. It is one of the basic building blocks of modern electronics. It is composed of semicondu ...

resistor A resistor is a passive two-terminal electronic component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active e ...

s, etc.) on

circuit board A printed circuit board (PCB), also called printed wiring board (PWB), is a laminated sandwich structure of conductive and insulating layers, each with a pattern of traces, planes and other features (similar to wires on a flat surface) ...

s. Several boards formed a discrete logic element of the machine, known as a '' module''. Overall machine cycle speed is strongly related to the signal path—the length of the wiring—requiring high-speed computers to make their modules as small as possible. This was at odds with the need to make the modules themselves more complex to increase functionality. By the late 1960s, individual components had stopped getting much smaller, so to increase the complexity of the machines, the modules would have to grow. In theory, this could slow the machine down due to signalling delays. Cray aimed to solve these contradictory problems by doing both; making each module larger and crammed with many more components, while at the same time making the computer as a whole smaller by packing the modules closer together inside the machine. Between the time the 7600 was developed and work on the 8600 began, there had been no process improvements in the components themselves, so any performance improvements had to come solely from packaging. For the new design, they used modules containing eight four-layer circuit boards about 8" by 6", resulting in a stack the size of a large textbook and using up about 3 kilowatts of power. The modules were then packed into a mainframe chassis that was comparatively tiny, a 16-sided cylinder about one meter (3') across and high, sitting on top of a ring of

power supplies A power supply is an electrical device that supplies electric power to an electrical load. The main purpose of a power supply is to convert electric current from a source to the correct voltage, current, and frequency to power the load. As a r ...

. The proposed design bears a strong resemblance to the later

, but even shorter and smaller in diameter."8600 prototype photo"
/ref> With all of this power being dissipated in such a small space, cooling was a major design issue. Cray's refrigeration engineer, Dean Roush, formerly of Amana, placed a sheet of copper inside each of the circuit boards, removing the heat to a copper block on one end where it was cooled by a

freon Freon ( ) is a registered trademark of the Chemours Company and generic descriptor for a number of halocarbon products. They are stable, nonflammable, low toxicity gases or liquids which have generally been used as refrigerants and as aerosol p ...

system. This further increased the weight and complexity of the modules, to the point where each one weighed about . The external cooling system was considerably larger than the machine itself. The electronic components were likewise improved over previous designs. The main

CPU A central processing unit (CPU), also called a central processor, main processor, or just processor, is the primary processor in a given computer. Its electronic circuitry executes instructions of a computer program, such as arithmetic, log ...

circuits moved to

ECL ECL may refer to: Science and technology * Electrochemiluminescence * Enhanced chemiluminescence * Emitter-coupled logic * Enterochromaffin-like cell Computing * ECL programming language, an extensible programming language * ECL (data-centric ...

-based logic, enabling a clock speed increase to 125MHz (8ns cycle time) from the 7600's 36.4MHz (27.5ns cycle time) an increase of about four times. Main memory was also moved to an ECL implementation and the machine was equipped with a whopping-for-the-times 256k-words (2 megabytes) standard. The design spread the memory across 64 banks for fast access at about 8 ns/word, even though the cycle time of any one bank was about 250 ns. A high-speed

core memory Core or cores may refer to: Science and technology * Core (anatomy), everything except the appendages * Core (laboratory), a highly specialized shared research resource * Core (manufacturing), used in casting and molding * Core (optical fiber), ...

with a 20 ns access (overall) was also designed as a backup to the semiconductor memory. Cray decided that the 8600 would include four complete CPUs sharing the

main memory Computer data storage or digital data storage is a technology consisting of computer components and recording media that are used to retain digital data. It is a core function and fundamental component of computers. The central processin ...

. To improve overall throughput, the machine could operate in a special mode that sent a single instruction to all four processors with different data. This technique, today known as

SIMD Single instruction, multiple data (SIMD) is a type of parallel computer, parallel processing in Flynn's taxonomy. SIMD describes computers with multiple processing elements that perform the same operation on multiple data points simultaneousl ...

, reduced the total number of memory accesses because the instruction was only read once, instead of four times. Each processor was about 2.5 times as fast as a 7600, so with all four running the machine as a whole would be about 10 times as fast, at about 100 MFLOPS. The government made it clear that all future computer purchases would require

ASCII ASCII ( ), an acronym for American Standard Code for Information Interchange, is a character encoding standard for representing a particular set of 95 (English language focused) printable character, printable and 33 control character, control c ...

processing. To meet this requirement, the 8600 used a

64-bit In computer architecture, 64-bit integers, memory addresses, or other data units are those that are 64 bits wide. Also, 64-bit central processing units (CPU) and arithmetic logic units (ALU) are those that are based on processor registers, a ...

word (eight eight-bit characters) instead of the earlier 60-bit word (ten six-bit characters) used in the 6600 and 7600. As in prior designs, instructions were "stuffed" into words, with each instruction taking up either 16- or 32-bits (up from 15/30). The 8600 no longer used the A or B registers as in previous designs, and included a set of 16 general-purpose X registers instead. A 6600/7600 Peripheral Processor system was used for I/O, largely unchanged. Some effort was made to help compatibility between the older machines and the 8600, but the change in word length made this difficult. Instead,

floating point In computing, floating-point arithmetic (FP) is arithmetic on subsets of real numbers formed by a ''significand'' (a signed sequence of a fixed number of digits in some base) multiplied by an integer power of that base. Numbers of this form ...

formats were retained, allowing Fortran code to port directly.

Company problems

In 1971, Control Data was undergoing a "belt tightening" due to the cost of an ongoing lawsuit against

IBM International Business Machines Corporation (using the trademark IBM), nicknamed Big Blue, is an American Multinational corporation, multinational technology company headquartered in Armonk, New York, and present in over 175 countries. It is ...

, and asked all divisions to reduce their payroll by 10%. Cray begged to Control Data to exempt his division so he could get the 8600 shipping. When Control Data refused this request, he cut his own pay to

minimum wage A minimum wage is the lowest remuneration that employers can legally pay their employees—the price floor below which employees may not sell their labor. List of countries by minimum wage, Most countries had introduced minimum wage legislation b ...

to solve the problem. By 1972, it appeared that even Cray's legendary module design abilities were failing him in the case of the 8600. Reliability was so poor that it appeared impossible to get a whole machine working. This was not the first time this had happened: on the 6600 project Cray had to start over from scratch, and the 7600 was in production for some time before it started working reliably. In this case Cray decided the current design was a dead-end, and told William Norris (CDC's CEO) that the only way forward was to redesign the machine from scratch. The finances of the company were dangerous, and Norris decided that he could not take the risk; Cray would have to continue with the current design. In 1972, Cray decided that he could not work under such conditions, and left CDC to form

Cray Research Cray Inc., a subsidiary of Hewlett Packard Enterprise, is an American supercomputer manufacturer headquartered in Seattle, Washington. It also manufactures systems for data storage and analytics. Several Cray supercomputer systems are listed i ...

(it was an amicable departure; Norris and other CDC staffers purchased some of the Cray Computer initial stock offering, which turned out to be a lucrative investment for them). For his new work he abandoned the multiprocessor concept, concerned that software of the era would be unable to take full advantage of the CPUs. He may have come to this conclusion after the

ILLIAC IV The ILLIAC IV was the first massively parallel computer. The system was originally designed to have 256 64-bit floating-point units (FPUs) and four central processing units (CPUs) able to process 1 billion operations per second. Due to budget cons ...

finally entered operation at about the same time, and proved to have disappointing performance. Team members convinced Norris that the 8600 could be completed even without Cray, and work continued at the Chippewa Lab. By 1974, the machine still didn't work correctly. Jim Thornton's competing

STAR A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

design had reached production quality at this point, and the 8600 project was then cancelled. In service STAR proved to have poor real-world performance, and when the

Cray-1 The Cray-1 was a supercomputer designed, manufactured and marketed by Cray Research. Announced in 1975, the first Cray-1 system was installed at Los Alamos National Laboratory in 1976. Eventually, eighty Cray-1s were sold, making it one of the ...

entered the market in 1976, CDC was quickly pushed from the supercomputer market. An effort was made to re-enter the market in the 1980s with the ETA-10, but this ended poorly.

Notes

*Gordon Bell puts the project start at 1968, while the only mention at the former Cray museum states it was 1970. *Quoted memory speed varies widely, with some sources suggesting a 22 ns cycle time for the semiconductor and 20 ns for the core, while other suggest the higher numbers used in this article. Nor is it clear if the core memory was designed as a backup, or that the semiconductor memory came along later.

Design

Company problems

Notes

References

Citations

Bibliography

Further reading