IBM 701

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.

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. Memory could be expanded to a maximum of 4096 words of 36 bits by the addition of a 2nd set of 72 Williams tubes or by replacing the entire memory with magnetic core memory. The CRT memory access time was 30uS. The core memory access time was 18uS.

Instructions were 18 bits long, single address.

Numbers were either 36 bits or 18 bits long.

The IBM 701 had only 2 programmer accessable registers:

1. The accumulator was 38 bits long (adding 2 overflow bits).
2. 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] (http://www-1.ibm.com/ibm/history/exhibits/701/701_customers.html).

External Links

• A Notable First: The IBM 701 (http://www-1.ibm.com/ibm/history/exhibits/701/701_intro.html)
• The Williams Tube (http://www.computer50.org/kgill/williams/williams.html)