Computer History MuseumSemiconductor History

1966 - Semiconductor RAMs Serve High-speed Storage Needs

Bipolar RAMs enter the computer market for high-performance scratchpad and cache memory applications.

Random Access Read-Write Memories (RAMs) store information that changes frequently and must be accessed quickly. Offering the lowest cost per storage bit, magnetic ferrite core arrays comprised the dominant RAM technology through the mid-1970s. Robert Norman patented a semiconductor static RAM design at Fairchild in 1963 that was later used by IBM as the Harper cell. In 1965 a cooperative development between Scientific Data Systems, Santa Monica, CA and Signetics produced a fully-decoded 8-bit bipolar device and later that year Components Division engineers Ben Agusta and Paul Castrucci developed the SP95, a 16-bit RAM for the IBM System/360 Model 95. A team led by Tom Longo at Transitron built the TMC3162 16-bit TTL scratchpad memory for the Honeywell Model 4200 minicomputer in 1966 that became the first widely second sourced semiconductor RAM. Fairchild (9033), Sylvania (SM-80), and TI (SN7481) also manufactured the design. 64-bit devices followed from IBM (cache memory chip), Fairchild (9035 and 93403), Intel (3101), and TI (SN7489).

In 1969 the IBM East Fishkill, NY facility produced a 128-bit device for the 1971 shipment of System/370 Model 145, the company's first commercial computer to employ semiconductor main memory. Using the 4100 (aka 93400) 256-bit TTL chip designed by H.T. Chua, Fairchild delivered semiconductor main memory systems for the Burroughs Illiac IV computer in April 1970. Using Douglas Peltzer’s Isoplanar oxide-isolated process that improved speed while consuming less silicon area, Fairchild's Bill Herndon designed a fast 256-bit TTL memory (93410) in 1971. The Cray 1 supercomputer introduced in 1976 used 65,000 Fairchild 1024-bit ECL RAM chips (10415) based on the Isoplanar process. Bipolar technology enabled faster computers but it took the MOS process to deliver low-cost solutions for widespread use in main memory and general-purpose applications. (1970 Milestone)

Contemporary Documents

Norman, Robert. "Solid State Switching and Memory Apparatus" U. S. Patent (3562721 Filed March 5, 1963, Issued February 9, 1971).

Perkins, H. A. and Schmidt, J. D. "An integrated semiconductor memory system," Fall Joint Computer Conference. AFIPS Proc., Vol. 27, (Nov. 1965) pp. 1053-1064.

Agusta, B., Bardell, P., Castrucci, P. "Sixteen bit monolithic memory array chip," IEEE Electron Devices Meeting, 1965 International Vol. 11 (1965) p. 39.

Agusta, B., Bardell, P., Castrucci, P., Henle, R., Pecoraro, R. "Monolithic Integrated Array Structure Including Fabrication and Package Therefor" U. S. Patent 3,508,209 (Filed March 31, 1966, issued April 21, 1970)

Potter, Gene B., Mendelson, Jerry, Sirkin, Sam. "Integrated scratch pads sire new generation of computers," Electronics Vol. 39, No. 7 (1966) pp: 118-126.

Rice, R., Sander, W. B., and Greene, F. S. Jr. "Design considerations leading to the ILLIAC IV LSI processor element memories," IEEE Journal Solid-State Circuits, Vol. SC-5, (Oct. 1970) pp. 174-181.

"Isolation Method Shrinks Bipolar cells for Fast, Dense Memories," Electronics (March 1, 1971) p. 76.

"IBM today introduced its first computer using a main memory made entirely of monolithic circuits," IBM Data Processing Division press release (September 23, 1970)

More Information

Pugh, E. W., Critchlow, D. L., Henle, R. A., Russell L. A. "Solid State Memory Development in IBM," IBM Journal of Research and Development.Vol. 25, No. 5 (September 1981) pp. 585-602.

Augarten, Stan. "The First 256-Bit Static RAM," State Of The Art: A Photographic History of the Integrated Circuit.(New Haven & New York: Ticknor and Fields, 1983) p.24.

Rappa, Michael R. The Development of Monolithic Integrated Circuit Memory Chips at IBM Corporation," Strategic Management Research Center, University of Minnesota (1984 ca.)

Pugh, Emerson W., Johnson, Lyle R., Palmer John H. IBM's 360 and Early 370 Systems (Cambridge, MA: The MIT Press, 1991) pp. 424-488

Bassett, Ross Knox. To the Digital Age. (Baltimore: The Johns Hopkins University Press, 2002) p. 102.