The IBM 604 was a control panel programmable Electronic Calculating Punch introduced in 1948, and was "a machine on which considerable expectations for the future of the business were pinned and in which a corresponding amount of planning talent was invested."
Most of the circuitry was based on modifications of circuit designs used in the earlier 603 Electronic Multiplier and was packaged in small one-tube-replaceable pluggable units, which made the product more easily manufactured and serviced. The calculation unit contained 1,250 tubes. Clock speed was increased from the 603's rate of 35kHz to 50 kHz. The 604 performed fixed point addition, subtraction, multiplication and division using BCD arithmetic.
Initial versions supported 40 program steps, and this was soon expanded to 60. Processing was still locked to the reader/punch cycle time, thus program execution had to complete within the time between a punched card leaving the read station and entering the punch station.
The 604 and a modified version, the 605, were used as components of the Card Programmed Electronic Calculators (CPC and CPC II). The 604 was also a component of the Test Assembly, a precursor to IBM's early computers. The circuit module design and packaging was also used for the IBM 650, a popular early computer.
An all-transistor version of the 604 was built and demonstrated in October 1954. Although it used 2000 transistors as opposed to 1250 tubes in the original, it occupied only half the volume, and used only 5% as much power. This was only an experimental machine, but its technology was used to build the IBM 608, which shipped in December 1957, and was the first solid-state computing product to be commercialized.
- IBM Archive: 1948
- Charles J. Bashe, Lyle R. Johnson, John H. Palmer, and Emerson W. Pugh, IBM's Early Computers, MIT Press, 1986, ISBN 0-262-02225-7, p. 61
- Pluggable Support for Electron Tube and Circuit US patent 2637763, filed July 9, 1948 , issued May 5, 1953, Ralph L. Palmer
- Weik, Martin H. (March 1961). A Third Survey of Domestic Electronic Digital Computing Systems: IBM 604 Section. Ballistic Research Laboratories (BRL). Report No. 1115. Contains about 4 pages of IBM 604 survey detail: applications, customers, specifications, and costs.
- Emerson W. Pugh, Lyle R. Johnson, John H. Palmer, IBM's 360 and early 370 systems, MIT Press, 1991, ISBN 0-262-16123-0, p. 34