Reference STATE OF THE ART Stan Augarten

ISBN 0-89919-195-9

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The Fourth Stage in Microprocessor Development
A 32-Bit Microprocessor


Built out of some 450,000 transistors, and one of the most sophisticated ICs yet produced, this chip is a 32-bit microprocessor. It contains about 9K 38-bit words of ROM and can multiply two 32-bit numbers in 1.8 millionths of a second. This IC represents the fourth stage in the development of microprocessors - a progression that began with the invention of the first 4-bit microprocessor at Intel and Texas Instruments back in the early 1970s (pp. 30 and 40).

  Every jump in the bit-processing ability of a microprocessor requires the installation of substantially greater circuitry on a chip. All else being equal, a 4-bit microprocessor calls for only four data paths, whereas an 8-bit version needs twice as many. Installing thirty-two data paths on an IC is obviously a vastly more complicated task. The chip on the right, for instance, took a squad of engineers eighteen months to design, and it is crisscrossed with some eighteen yards of microscopically thin tungsten (rather than aluminum) interconnections.

  This IC was created for anew machine, the HP9000 desk-top engineering computer, and is the cornerstone of a family of ultrasophisticated chips that includes a 128K RAM, a 660K ROM, a timer, and input/output processor, and a dynamic memory controller that allows up to twenty 128K RAMs and eight 640K ROMs to be plugged into the computer. Assembled on a single circuit board, these six basic chips comprise a computer whose power exceeds that of some mainframe computers.

This IC and one by Bell Labs were the first single-chip 32-bit microprocessors. The dense grid on the right is a ROM capable of storing 9.2K words, each 38 bits ling; the less dense grid on the opposite side is a register. The square grid directly beneath the register is the arithmetic and logic unit, or ALU, the device that performs the computations. The irregular circuits in the center of the chip make up the programmed logic array, or PLA, the component that decodes the instructions stored in ROM and controls the chip. The rectangular features on the chip's perimeter are test devices, spatial resolution patterns, and fabrication alignment marks. Actual size: 0.250 x 0.253 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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