The Core Memory Project



NCR Century Series
Special Thanks To

Walter Niblick for his contribution to this page.

Ian Ormerod for his contribution to this page.

NCR Century
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NCR Century Series 

Product History

With its new Century Series computers NCR has staked a claim for a substantially larger share of the total computer market with the worldwide introduction of a major new familyNCR Century of data processing systems. The Century program represented an investment of $154 million in research, engineering, software, new production facilities and equipment, and in training of marketing and service personnel.

The lower-priced members of the Century family have been oriented toward the “mass computer market”, including first-time computer users. In addition to high-performance equipment at relatively low cost, this market also required ready-to-use supporting software, beamed at the specific requirements of different lines of business.

To this end NCR conducted in-depth systems studies in financial institutions, the retailing industry, industrial companies, insurance companies, government offices, hospitals, hotels, motels, schools, law enforcement agencies and other fields. These studies provided new guidelines for developing a wide range of standard application “packages” designed to simplify moving up to a computer system from punched card or other mechanical business equipment. Primary emphasis has been placed on insuring that the new computer family’s basic software would be ready for customer use well in advance of first equipment deliveries.

The first models of the Century Series have been available for internal use for over a year before entering market. As a result, the compiler and the operating software systems have for the most part already been checked out. The Company itself was using 64 of the new systems, prior to customer deliveries, for training of service and support personnel, further software checkout, and customer use at regional checkout centers.

The educational program in preparation for the introduction of the new family of computers was the most extensive in the corporation’s history. Among marketing personnel this in-depth program has included not only data processing specialists but hundreds of customer support personnel and technical service representatives.

A comprehensive educational service has been provided for all Century users, including their systems personnel, programmers and operators. NCR was also establishing new regional center facilities for checkout customer programs and for providing other ongoing assistance.

Nearing completion a new 300,000-square-foot manufacturing plant was built at San Diego, California, to augment NCR’s electronics production facilities at Hawthorne, California and Dayton, Ohio. Manufacturing of the Century family also is being carried out at NCR factories in Dundee, Scotland, and Augsburg, Germany.


Century Hardware

The versatile new computers were based on significant design advances in ultra-high-speed thin-film memories, monolithic integrated circuitry, disc memory innovations, and automated production techniques. These features provided users with greater performance than ever before available in computer systems in their price range.

The Century Series was a full family of compatible systems designed to meet the data processing needs of a wide range of users. This includes the first-time computer users as well as the highly advanced users, employing real-time and multiprogramming concepts. The systems’ capabilities cover all types of business data processing and also special scientific applications. This was by far the largest product development effort ever undertaken in NCR’s 84-year history.

Initially, NCR was releasing two lines of the new computer family - the Century 100 and the larger Century 200. The new computer family also included  more powerful multiprocessing and time-sharing models scheduled for future release. These will put NCR in the sector of the computer market it was not active before. All models in the entire Century Series have on-line, real-time capabilities. A full line of peripheral equipment including disc units, card readers, printers, magnetic tape handlers, and a new high-capacity CRAM (Card Random Access Memory) was also introduced by the Company.


System Flexibility

One of the most significant features of the Century Series was its great flexibility, which permitted the user to modify and expand his system as his data processing needs change and grow. The Century user can easily increase the capacity and power of the processor, add or combine a variety of peripheral devices, or move up to a larger basic system without costly reprogramming. Both software and hardware are compatible throughout the entire computer family. The compatibility of the Century family was a result of a highly developed “systems architecture” under which NCR designers applied significant advances in technology to meet the demanding design objectives.


Thin-Film Rod Memory

One of the technical breakthroughs was NCR’s development of a unique thin-film rod memory, the most advanced memory in use in any commercial computer in its price range. It employed thousands of tiny “whiskers” in place of the usual doughnut-shaped ferrite cores. Each of these hair like rods was only 1/10 inch long and was coated with a thin film of magnetic material. The Company’s proprietary methods of automatically fabricating and assembling the short rods into memories have contributed importantly to the Century Series’ outstanding cost/performance ratio. The same basic memory module was used throughout the entire computer family.

It operates at 800 nanoseconds cycle time (800 billionths of a second) and is in the form of modules which can be expanded. The basic Century 100 has a memory of 16,000 characters which is expandable to 32,000. A Century 200 system can have a memory capacity of up to 524,000 characters.


Disc Storage

Every Century system included two discs which feature significant design improvements. In addition to providing ultra-fast, high-capacity data storage for even the lowest-cost member of the family, the Century disc was used as a reservoir for the storage of operating software. This concept makes use of inexpensive disc storage in place of relatively expensive main memory for interim storage in many computer functions. This frees the main memory and greatly extends program performance and compatibility throughout the family. Each of the discs stored more than four million bytes of information.

Because of a breakthrough in the manufacture of low-cost read-write heads, coupled with a new type of head-positioning unit, access time to information was considerably faster than any other removable disc in its price range. Average access time was 42 milliseconds. Rate of data transfer was 108,000 bytes per second with a Century 100 and up to 180,000 with a Century 200.

The two removable disc packs were made up of three discs each. Seventy two read-write heads serve each disc pack, providing 12 times as many heads per disc surface as other systems. The multiple-track heads provide immediate access to 1/16 of the total file (more than half-a-million bytes), compared with 1/200 on typical units available those days.

The discs were unique in that they are metal-plated instead of oxide-coated, providing an exceptionally clean and long-wearing surface.


Integrated Circuits

Another major area of advanced technology incorporated in the Century Series was its use of monolithic integrated circuits throughout the system, including peripheral units as well as the central processor. Only one* type of integrated circuit was used throughout the new family of machines. The circuits were mounted in standardized cords and only six different types of cards make up 80 percent of the logic circuitry. There were only 120 different card types in the entire system, a fraction of the number used in most computer systems those days.

The simplicity of circuitry design and standardized mass fabrication were key factors in the outstanding cost/performance of the systems, NCR stated. In addition, this simplified servicing of the computers and greatly reduces the spare parts inventory that must be kept in the field.



All Century computers used the international and American (ASCII) standard codes for information interchange.


*) Expert’s Remark:

“I am quite confident in the 3 types of IC's as I even remember the numbers of each one. It may be a "nit pick", but that's the way Engineers are. I may reverse the definitions of the NCR 74 and NCR 80, but the two descriptions are correct. The NCR 74 had four logic gates of two inputs each. We used these chips for simple logic, flip-flops, register inputs, etc. The specific card I remember was the Transfer card. It had 4 groups of 4 gates each. Each group of 4 had a common input with one input left on each gate for data. These were primarily used for register inputs: data; address; etc. The NCR 80 included two general logic gates of 4 independent inputs each. As I recall we used two of these on a Logic card for a total of 4 gates of 4 independent inputs each. The NCR 94 was an interface device, also of two inputs each. This might be the one that was not considered in the statement that we only used two IC's. The other gates had a threshold voltage of 0.8 volts. That was not high enough to give us any noise immunity on incoming signals. The NCR 94 had an input threshold of 1.4 volts on at least one of the inputs. That was a level of noise immunity that was required in many applications, but the input with the higher threshold voltage also had a longer delay time. We were running into infrequent/random failures on the 615-300 that were tough to identify, but when we started putting the same devices on 4"x8" cards (instead of 4"x4"), and using them in a 9x8 cross bar - then we discovered that it took so much power to energize each gate that when enough of them switched at once it was pulling down the ground level. This started giving us false positive logic signals. This did not really become clear until the 618-930. All the modules worked asynchronously in the 618 memory units. When we had a card that shared control for different input ports, or different output modules, then when one bank of logic switched it would lower the ground level on the whole card. It was impossible to time around this effect with asynchronous logic. That's what drove our need to add internal ground planes to the cards, which we had not identified as a requirement on the old 4x4's or the early 4x8's.

This was the first NCR system (Century series) that had the NAND/NOR type logic.

Jim Taylor


Related Materials

Click the name for details Integrated Circuit Description: QUAD 2-INPUT NAND 007-1667401.
Click the name for details Integrated Circuit Description: DUAL, 4-INPUT NAND GATE, OPEN COLLECTOR 007-1668001.
Click the name for details Integrated Circuit Description: QUAD 2-INPUT AMP 007-1669401.



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