The Third Generation, 1965-1970: The Integrated Circuit

One of the most abundant elements in the earth's crust is silicon, a nonmetallic substance found in common beach sand as in practically all rocks and clay. The element has given rise to the name " Silicon Valley" for Santa Clara County, which is about 30 miles south of San Francisco. In 1965 Silicon Valley became the principal site of the electronics industry making the so-called silicon chip.

In 1959, engineers at Texas Instruments invented the integrated circuit (IC), a semiconductor circuit that contains more than one transistor on the same base (or substrate material) and connects the transistors without wires. The first IC contained only six transistors. By comparison, the Intel Pentium Pro microprocessor used in many of today's high-end systems has more than 5, 5 million transistors, and the integral cache built into some of these chips contains as many as an additional 32 million transistors. Today, many ICs have transistor counts in the multimillion ranges.

An integrated circuit is a complete electronic circuit on a small chip of silicon. The chip may be less than 1/8 inch square and contains hundreds of electronic components. Beginning in 1965, the integrated circuit began to replace the transistor in machines now called third-generation computers.

Silicon is used because it is semiconductor. That is, it is a crystalline substance that will conduct electric current when it has been " doped" with chemical impurities shot into the latticelike structure of the crystal. A cylinder of silicon is sliced into wafers, each about 3 inches in diameter, and wafer is " etched" repeatedly with a pattern of electrical circuitry.

Integrated circuits entered the market with the simultaneous announce­ment in 1959 by Texas Instruments and Fairchild Semiconductor that they had each independently produced chips containing several complete electronic circuits. The chips were hailed as generation breakthrough because they had four desirable characteristics: reliability, compactness, low cost, low power use.

In 1969, Intel introduced a lK-bit memory chip, which was much larger than anything else available at the time. (IK bits equals 1, 024 bits, and a byte equals 8 bits. This chip, therefore, stored only 128 bytes-not much by today's standards.) Because of Intel's success in chip manufacturing and

design, Busicomp, a Japanese calculator manufacturing company, asked Intel to produce 12 different logic chips for one of its calculator designs. Rather than produce 12 separate chips, Intel engineers included all the functions of the chips in a single chip.

In addition to incorporating all the functions and capabilities of the 12- chip design into one multipurpose chip, the engineers designed the chip to be controlled by a program that could alter the function of the chip. The chip then was generic in nature, meaning that it could function in designs other than calculators. Previous designs were hard-wired for one purpose, with built-in instructions; this chip would read from memory a variable set of instructions that would control the function of the chip. The idea was to design almost an entire computing device on a single chip that could perform different functions, depending on what instructions it was given.

The third generation saw the advent of computer terminals for communicating with a computer from a remote location.

Operating systems (OS) came into their own in the third generation. The OS was given complete control of the computer system; the computer operator, programmers, and users all obtained services by placing requests with the OS via computer terminals. Turning over control of the computer to the OS made possible models of operation that would have been impossible with manual control. For example, in multiprogramming the computer is switched rapidly from program to program in round-robin fashion, giving the appearance that all programs are being executed simultaneously.

An important form of multiprogramming is time-sharing, in which many users communicate with a single computer from remote terminals.