Reference STATE OF THE ART Stan Augarten

ISBN 0-89919-195-9

Photo of
One of the Most Popular 8-bit Microprocessors
The Z-80


Zilog's founding was a typical Silicon Valley story. A group of entrepreneurially minded engineers quick their jobs, obtained venture capital, and opened up their own shop more or less a stone's throw away from their old employer - in this case Intel, which was established by three men who left Fairchild, which was started by twelve engineers who left Shockley Transistor, which was founded by William Shockley of Bell Labs. Zilog's founders included two of the most talented IC designers in the United States: Frederico Faggin, who had helped create the Intel 4004, the first microprocessor (p. 30), and Masatoshi Shima, who had been the chief designer of the enormously successful Intel 8080 (p. 36).

  The first product from Zilog (an acronym in which the Z stands for "the last word," the i for integrated, and the log for logic - hence, the last word in integrated logic) was the Z-80, a powerful 8-bit microprocessor unabashedly based on the 8080. The two chips have the same basic architecture and instruction set (the code that allows a microprocessor to carry out its chores) and are electronically interchangeable. But the Z-80 is a vast improvement over its predecessor, containing, in addition to the circuitry of the 8080, its own clock, system controller, dynamic memory refreshers, and other elements.

  As a result, the Z-80 is very widely used and has superseded the 8080 in many machines. It is found in person computers, smart typewriters, medical equipment, airplane navigation controls, and video games. (Pac-Man uses and advanced version of it.) In and of itself, however, a powerful and versatile microprocessor is not necessarily an advantage. A microprocessor is like a car engine: the best isn't always the one with the most zoom and push, but the one that does the best job for the right price.

Several Z-80s are seen here on a wafer, a chessboard-like slice of silicon that contains hundreds of chips. Wafers are cut up into separate ICs and place into individual packages, which are then plugged into circuit boards. The Z-80 can control up to 64K bytes of memory and add two 8-bit numbers in one millionth of a second; it multiplies by repeated addition. The purple color is the result of a bright light being shone onto the wafer. Actual size of the Z-80: 0.157 x 0.167 inches. Photo of


©Copyright Stan Augarten
This book is provided for general reference. The National Museum of American History and the Smithsonian Institution make no claims as to the accuracy or completeness of this work.

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