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CDC 6000 series were a family of mainframe computers manufactured by Control Data Corporation in the 1960s. It consisted of CDC 6400, CDC 6500, CDC 6600 and CDC 6700 computers, which all were extremely rapid and efficient. Each was a large, solid-state, general-purpose, digital computer that performed scientific and business data processing as well as multiprogramming, multiprocessing, time-sharing, and data management tasks under the control of the operating system called SCOPE (Supervisory Control Of Program Execution).

The CDC 6000 series computer is composed of four main functional devices: the central memory, one or two high speed central processors, seven to ten peripheral processors, and a display console. The four computer types differ primarily in the number of and kind of central processor. It had a distributed architecture and was a reduced instruction set (RISC) machine many years before such a term was invented.

Central processor

The central processor is a high-speed arithmetic unit that functions as the workhorse of the computer. It performs most of the addition, subtraction, and logical operations and all of the multiplication, division, incrementing, indexing, and branching instructions for user programs. Note that in the CDC 6000 architecture, the central processing unit performed no I/O operations. I/O was totally asynchronous, and performed by peripheral processors.

The central processor used in the CDC 6400 computer included 24 operating registers linked to an arithmetic section that performs one arithmetic instruction at a time. That is, it can add, then subtract, then add again, and then multiply. The CDC 6500 was identical to the 6400, but included two identical 6400 CPUs. Thus the CDC 6500 could nearly double the computational throughput of the machine.

The CDC 6600 computer, like the CDC 6400, has just one central processor. However, its central processor offers much greater efficiency. Its 24 operating registers, used for such information as operating codes, operand addresses and results, are linked to 10 individual arithmetic sections, each of which performs one function. All sections can operate simultaneously. The CDC 6600 can perform up to ten arithmetic functions at the same time, however, since it has only one section for division and one for Boolean operation, it cannot perform two division or two Boolean operations simultaneously. Because its central processor includes two multiplication and two incrementation sections, the CDC 6600 can perform two multiplications or incrementing operations at the same time.

The CDC 6700 computer combines the best futures of the other three computers. Like the CDC 6500, it has two central processors. One is similar to CDC 6400/CDC 6500 central processor with the unified arithmetic section; the other is the same as the more efficient CDC 6600 central processor. The combination makes the CDC 6700 the fastest and the most powerful of the four CDC 6000 series.

Central memory

In all the CDC 6000 series computers, the central processor communicates with up to seven simultaneously active programs (jobs), which reside in central memory. Instructions from these programs are read into the central processor registers and are executed by the central processor at scheduled intervals. The results are then returned to central memory.

Information is stored in central memory in the form of words. The length of each word is 60 binary digits (bits). The highly efficient address and data control mechanisms involved permit a word to be moved into or out of central memory every 100 nanoseconds.

An extended core storage unit (ECS) provides additional memory storage and enhances the powerful computing capabilities of the CDC 6000 series computers.

Peripheral processors

The central memory shares access to central memory with ten peripheral processors. Unlike the central processor, each peripheral processor is an individual computer with its own memory. Peripheral processors are used primarily for input/output, the transfer of information between central memory and peripheral devices such as disks and magnetic tape unit. They relieve the central processor of all input/output tasks, so that it can perform calculations while the peripheral processors are engaged in input/output functions. This feature promotes rapid overall processing of user programs. Each peripheral processor can add, subtract, and perform logical operations. Each executes SCOPE routines independently of the others.

Data channels

For input or output, each peripheral processor accesses a peripheral device over a communication link called a data channel. One peripheral device can be connected to each data channel; however, a channel can be modified with hardware to service more than one device.

Each peripheral device can communicate with any peripheral device if another peripheral processor is not using the data channel connected to that device. In other words, only one peripheral processor at a time can use a particular data channel.

Display console

In addition to communication between peripheral devices and peripheral processors, communication takes place between the computer operator and the operating system. This was made possible by the computer console, which had two CRT screens.

The console screens were calligraphic, not raster based. Analog circuitry actually steered the electron beams to draw the individual characters on the screen. One of the peripheral processors ran a dedicated program called "DSD" (Dynamic System Display), which drove the console. Coding in DSD needed to be fast - as it needed to continually redraw the screen fast enough to avoid visible flicker.

DSD displayed information about the system and the jobs in process. The console also included a keyboard through which the operator could enter requests to modify stored programs and display information about jobs in or awaiting execution.

A full screen editor, called "026" (after the IBM card punch of the same name), could be run on the operator console. This text editor appeared in 1966 - years before full screen editing was available on other systems. (Unfortunately it took CDC another 15 years to offer FSE - a full-screen editor for normal time-sharing users on CDCs network operating system.)

Minimum configuration

The minimum hardware requirements of a CDC 6000 series computer system consists of the computer, including 32,768 words of central memory storage, any combination of disks, disk packs or drums to provide 24 million characters of mass storage, a punched card reader, punched card punch, printer with controllers, and two 7-track magnetic tape units. Larger systems can be obtained by including optional equipment such as: additional central memory, extended core storage, (ECS), additional card readers, punches, printers, and tape units. Graphic plotters and microfilm recorders are also available.

History

The first member of the CDC 6000 series was the first supercomputer CDC 6600, designed by Seymour Cray and James E. Thornton in Chippewa Falls, Wisconsin. It was introduced in September, 1964 and performed up to three million instructions per second, three times faster than the IBM Stretch, the speed champ for a couple years. It remained the fastest machine for five years until the CDC 7600 was launched. The machine was Freon refrigerant cooled. Control Data manufactured about 100 machines of this type, selling for $6 to $10 million each.

The first successor of the CDC 6600 was the CDC 6400, a slower but cheaper version, delivered in April, 1966. Then followed the machines with double central processors, the CDC 6500, designed principally by James E. Thornton, in October, 1967 and the CDC 6700, in October, 1969.

Subsequent modifications to the series in 1969 included the extension to 20 peripheral and control processors with 24 channels. Control Data also marketed a CDC 6400 with a smaller number of peripheral and control processors, the CDC 6415-7 with 7 peripheral processors to reduce cost.

References

CDC hardware Microsoft on CDC computers] Supercomputers

 

This article is licensed under the GNU Free Documentation License. It uses material from the "CDC 6000 series".

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