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Thursday, May 27, 2010

The History of NSA Computers Well up until 1964 at least Part I

The History Of NSA Computers. Well, Up Until 1964 At Least. Part I.

Alex Trent
Staff Writer

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Recently a formerly classified document was declassified describing how the NSA used computers to crack codes.

Part I: ATLAS I and ABEL

The History Of NSA Computers. Well, Up Until 1964 At Least. Part I.
The History Of NSA Computers. Well, Up Until 1964 At Least. Part I.

Before the NSA, its predecessors used punch card systems for about 15 years, beginning in 1935. There were 750 such systems in use by the end of World War II. Several types of punched-card devices were used: tabulators, collators, sorters, reproducers, and the keypunch. As we know now, the use of punched-card equipment would not last for ever. Finally, in December of 1950, the first real computer arrived.

ATLAS I's beginning can be traced back to a series of lectures in 1946 at the Moore School of Electrical Engineering on electronic computing. The Navy had a young mathematician named LCDR James T. Pendergrass who attended. The lectures inspired Pendergrass to suggest that the Navy should have a computer. The computer was constructed by a contractor for the Navy at a cost of $950,000, it had 2700 tubes and used parallel circuitry.

Originally the computer was intended to have 36-bit words, but the design eventually used was 24-bit words. These words would be stored on a magnetic drum that would hold 16,384 of them. The drum had a fascinating feature called an "interlace" where it allowed memory to be accessed by a plugboard system that gave programmers the freedom to design programs that could jump one step forward or backward in memory using pre assigned addressing via the plugboard. Access time was as low as 32 microseconds using this system. Unfortunately, the average access time was 8,500 microseconds and in more proving situations, could jump as high as 17,000 on occasion. Later on, the interlace was upgraded to support jumping in steps larger than one in memory.

ATLAS I was not the only computer available to the Navy at the time. ABEL, was created to serve as a training machine for new programmers. Although logically identical to ATLAS I, ABEL was was several hundred times slower and only supported 2,047 words on its drum. After presentation to the Albert Einstein High School in 1963, ABEL was permanently dismantled.

Three years after ATLAS I's initial arrival, a second computer, identical to ATLAS I arrived in May of 1953. Both machines were upgraded in 1956 with high-speed core storage units of 4,096 word capacity. Before the high-speed core memory was installed, programmers used the interlace function excessively. Now they could store constants in the high-speed memory for quick access. Only three more years later, both machines were removed from operation. One was salvaged for parts and the other was shipped to a NATO Anti-Submarine Research Center in Italy.

If ATLAS I had a design flaw it was its lack of magnetic tape storage. When the machines were dismantled, this was likely the reason. Other than that the machines were operational above 90% of the time. The lack of tape storage restricted their used to problems with small volumes of data.

This article is the first in a series of articles on NSA computers up until 1964.
For more in depth reading:

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