Metal mask plot for 16-bit RAM. Image from a 1967 TV documentary
Credit: Fairchild Camera & Instrument Corporation.

Commonly abbreviated to RAM, Random Access Read-Write Memories store information that changes frequently and must be accessed quickly. Magnetic ferrite core arrays comprised the dominant RAM technology through the mid-1970s as they provided the lowest cost per storage bit. Operations requiring faster access times held data temporarily in ranks of semiconductor flip-flop circuits called registers. Each flip-flop stored one bit of data and consumed six transistors. IBM Components Division designed one of the first dedicated semiconductor RAMs in 1966; a 16-bit bipolar chip for System/360 Model 95. Also in 1966, Transitron engineers led by Tom Longo built the TMC3162 16-bit TTL scratchpad memory for control storage in the Honeywell Model 4200 minicomputer. Fairchild (9033), Sylvania (SM-80), and TI (SN7481) alternated-sourced the design. IBM followed with a 64-bit version and by 1969 Fairchild (9035 and 93403), Intel (3101), and TI (SN7489) produced 64-bit devices as standard catalog products.

Using the 4100 (also called 93400) 256-bit TTL chip designed by H.T. Chua, Fairchild delivered the first semiconductor main memory systems for the Processor Element Memory (PEM) of the Burroughs Illiac IV computer in April 1970. Using Douglas Peltzer’s Isoplanar oxide-isolated bipolar process, Bill Herndon designed a higher-speed 256-bit TTL memory (Fairchild 93410) in 1971. By improving speed while consuming less silicon area, the Isoplanar process also yielded very-high performance ECL compatible devices. (1965 Milestone) The Cray 1 supercomputer introduced in 1976 used 65,000 Fairchild 1024-bit ECL RAM chips. Bipolar technology enabled faster computers but it took the MOS process to deliver low-cost solutions for computer main memory and general-purpose applications. (1970 Milestone)