IBM 701

IBM 701 Electronic Data Processing Machine
Company type	Computer system
Industry	Computing / Electronics
Predecessor	Defense Calculator
Founded	May 21, 1952; 74 years ago
Founder	Jerrier Haddad, Nathaniel Rochester
Fate	Superseded by IBM 704
Successor	IBM 704
Headquarters	New York, United States
Area served	Worldwide (scientific and defense institutions)
Key people	Jerrier Haddad, Nathaniel Rochester
Products	Scientific computer, mainframe computer
Owner	IBM
Parent	IBM

IBM 701 Electronic Data Processing Machine

The IBM 701 Electronic Data Processing Machine, originally named the Defense Calculator, was IBM’s first commercially available scientific computer and the company’s initial mass-produced mainframe computer series, unveiled on May 21, 1952. Its design, led by Jerrier Haddad and Nathaniel Rochester, drew inspiration from the IAS machine developed at Princeton.

As the pioneering model in the IBM 700/7000 lineup, the 701 served as IBM’s premier computing platform until the launch of the IBM System/360 in 1964. The business-oriented equivalent was the IBM 702, while the more economical IBM 650 gained recognition as the first computer to be produced on a large scale, broadening IBM’s presence in general-purpose computing.

History

The IBM 701 vied with Remington Rand's UNIVAC 1103 in the field of scientific computation. In early 1954, the Joint Chiefs of Staff conducted a comparative evaluation of both machines for a Joint Numerical Weather Prediction initiative. While their processing speeds were closely matched, IBM’s system was preferred due to its substantially quicker input/output mechanisms.

A total of nineteen IBM 701 units were deployed. The inaugural system was installed at IBM's New York headquarters, eight were allocated to aerospace companies, and others found use at institutions such as the Lawrence Livermore National Laboratory, where it expedited calculations related to nuclear weaponry.

The oft-quoted statement, "I think there is a world market for maybe five computers," is incorrectly attributed to IBM chairman Thomas Watson Sr.; it more likely originated from his son, Thomas Watson Jr., who in 1953 remarked that after engaging with twenty prospective customers for the IBM 701, IBM secured orders for eighteen machines—far exceeding initial expectations.

In 1953, leasing fees for the IBM 701 ranged from about $12,000 to $15,000 monthly for a single 40-hour shift, with an additional shift raising rental costs to approximately $20,000 per month.

The successor to the IBM 701 was the index register-enabled IBM 704, introduced four years later. The IBM 704 was not backward compatible with its predecessor due to its expanded 36-bit instruction format and adoption of magnetic-core memory, enabling advanced functionalities.

Social impact

In 1952, IBM partnered with linguists from Georgetown University to pioneer early machine translation software. On January 7, 1954, their team developed an experimental program allowing the IBM 701 to perform Russian-to-English translation in what became known as the Georgetown–IBM experiment. The Mark 1 Translating Device, created for the US Air Force, achieved its first automated Russian-to-English translation in 1959 and was publicly showcased in 1964.

That same year, researchers utilized the IBM 701 to simulate millions of blackjack hands, formulating optimal strategies that remain influential.

The IBM 701 also played a role in early developments in artificial intelligence through Arthur Samuel's checkers-playing program demonstrated in 1956. This public exhibition marked a key achievement in AI history. Later, in 1962, an IBM 7094 computer defeated Robert Nealey—a self-declared checkers champion—highlighting significant progress in AI technologies by IBM.

At the University of California Radiation Laboratory at Livermore, a language compilation and runtime environment named KOMPILER was developed specifically for the IBM 701. Additionally, Speedcoding, created by John Backus in 1953 for this machine, represented IBM’s first high-level programming language supporting floating-point operations. Backus subsequently developed the Fortran compiler for the IBM 704 model.

Hardware Configuration

The IBM 701 system comprised the following components:

IBM 701 - Analytical Control Unit (central processing unit)
IBM 706 - Electrostatic Storage Unit featuring 2048 words of Williams tube memory
IBM 711 - Punched Card Reader with a throughput of 150 cards per minute
IBM 716 - Printer capable of producing 150 lines per minute
IBM 721 - Punched Card Recorder operating at 100 cards per minute
IBM 726 and IBM 727 - Magnetic Tape Readers/Recorders supporting densities of 100 and 200 bits per inch respectively
IBM 731 - Magnetic Drum Reader/Recorder
IBM 736 and IBM 741 - Power Frames #1 and #2
IBM 737 - Magnetic Core Storage Unit containing 4096 words of core memory with a 12-microsecond cycle time
IBM 740 - Cathode Ray Tube Output Recorder
IBM 746 - Power Distribution Unit
IBM 753 - Magnetic Tape Control Unit, capable of managing up to ten IBM 727 tape drives

The overall system weight varied based on the specific configuration but was approximately .

Memory

Employing vacuum tube logic circuits, the system utilized electrostatic memory through 72 Williams tubes, each holding 1024 bits, which combined to provide a total of 2048 words, each consisting of 36 bits. Each Williams tube had a diameter of three inches. Memory capacity could be expanded to 4096 words by adding an additional set of tubes or later by substituting with magnetic-core memory. Both Williams tube and core memory operated with a cycle time of twelve microseconds. The Williams tube required periodic refresh operations integrated within the machine's timing sequence. Performing an addition involved five cycles of twelve microseconds each (including two refresh cycles), while multiplication or division took thirty-eight cycles, totaling approximately 456 microseconds. Secondary storage was provided by magnetic drum and tape devices.

Instruction Set

Instructions were encoded in an eighteen-bit format with a single address field:

Sign bit (1 bit) indicating whole or half-word operand addressing
Operation code (5 bits) allowing for thirty-two distinct instructions
Address field (12 bits) supporting up to 4096 half-word addresses

Data values were represented as signed magnitude numbers in either thirty-six or eighteen bits using fixed-point notation. Full word precision corresponded to roughly ten decimal digits.

The IBM 701 featured two registers accessible to programmers:

An accumulator register with thirty-eight bits, including two overflow indicator bits
A multiplier/quotient register consisting of thirty-six bits

Peripherals

The Magnetic Drum Reader/Recorder was incorporated following John von Neumann's advice to alleviate the demands on high-speed input/output operations.

Magnetic tape drives were initially developed for the Tape Processing Machine (TPM) before being adapted for use with the IBM 701.

IBM 701 Customers

IBM World Headquarters, New York, New York (1952)
University of California, Los Alamos, New Mexico (1953)
Lockheed Aircraft Company, Glendale, California (1953)
National Security Agency, Washington, D.C. (1953)
Douglas Aircraft Company, Santa Monica, California (1953)
General Electric Company, Lockland, Ohio (1953)
Convair, Fort Worth, Texas (1953)
U.S. Navy, Inyokern, California (1953)
United Aircraft, East Hartford, Connecticut (1953)
North American Aviation, Santa Monica, California (1953)
Rand Corporation, Santa Monica, California (1953)
Boeing Corporation, Seattle, Washington (1953)
Douglas Aircraft Company, El Segundo, California (1954)
Naval Aviation Supply, Philadelphia, Pennsylvania (1954)
University of California, Livermore, California (1954)
General Motors Corporation, Detroit, Michigan (1954)
Lockheed Aircraft Company, Glendale, California (1954)
U.S. Weather Bureau, Washington D.C. (1955)
Dupont Central Research, Wilmington, Delaware (1954)

References

Notes

External links

IBM 701: A Significant Milestone (IBM Archives)
Gene Amdahl Oral History Interview Charles Babbage Institute, University of Minnesota, Minneapolis. Amdahl reflects on his contributions to the design of multiple IBM computers including the 701, IBM 704, and STRETCH, as well as his collaboration with Nathaniel Rochester and IBM’s design leadership.
The Williams Tube