IBM 701
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The IBM 701, known as the Defense Calculator while in development, was announced to the public on April 29, 1952, and was IBM’s first commercial scientific computer[1]. Its business computer siblings were the IBM 702 and IBM 650.
The system used electrostatic storage, consisting of 72 Williams tubes with a capacity of 1024 bits each, giving a total memory of 2048 words of 36 bits each. Each of the 72 Williams tubes was three inches in diameter. Memory could be expanded to a maximum of 4096 words of 36 bits by the addition of a second set of 72 Williams tubes or by replacing the entire memory with magnetic core memory. The tube memory access time was 30 microseconds. The core memory access time was 18 microseconds. A whole word addition operation took 5 12-microsecond machine cycles (60 microseconds), multiply and divide operations each took 38 12-microsecond machine cycles (456 microseconds).
Instructions were 18 bits long, single address.
- Sign (1 bit) - Whole word (-) or Half word (+) operand address
- Opcode (5 bits) - 32 instructions
- Address (12 bits) - 4096 Half word addresses
Numbers were either 36 bits or 18 bits long, signed magnitude, fixed point.
The IBM 701 had only 2 programmer accessible registers:
- The accumulator was 38 bits long (adding 2 overflow bits).
- The multiplier/quotient was 36 bits long.
The IBM 701 system was composed of the following units:
- IBM 701 - Analytical Control Unit (CPU)
- IBM 706 - Electrostatic Storage Unit (2048 words of CRT Memory)
- IBM 711 - Punched Card Reader (150 Cards/min.)
- IBM 716 - Printer (150 Lines/min.)
- IBM 721 - Punched Card Recorder (100 Cards/min.)
- IBM 726 - Magnetic Tape Reader/Recorder (100 Bits/inch)
- IBM 727 - Magnetic Tape Reader/Recorder (200 Bits/inch)
- IBM 731 - Magnetic Drum Reader/Recorder
- IBM 736 - Power Frame #1
- IBM 737 - Magnetic Core Storage Unit (4096 words of Core Memory)
- IBM 740 - Cathode Ray Tube Output Recorder
- IBM 741 - Power Frame #2
- IBM 746 - Power Distribution Unit
- IBM 753 - Magnetic Tape Control Unit (controlled up to ten IBM 727s)
Nineteen IBM 701 systems were installed [1]. The University of California at Livermore developed a language compilation and runtime system called the KOMPILER for their 701. A Fortran compiler was not released by IBM until the IBM 704.
The successor of the 701 was the index register-equipped IBM 704, introduced 4 years after the 701. The 704 was not compatible with the 701, however, as the 704 increased the size of instructions from 18 bits to 36 bits to support the extra features.
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[edit] Bibliography
- Charles J. Bashe, Lyle R. Johnson, John H. Palmer, Emerson W. Pugh, IBM's Early Computers (MIT Press, Cambridge, 1986)
- Cuthbert C. Hurd (editor), Special Issue: The IBM 701 Thirtieth Anniversary - IBM Enters the Computing Field, Annals of the History of Computing, Vol. 5 (No. 2), 1983
