Reference STATE OF THE ART Stan Augarten

ISBN 0-89919-195-9

Photo of
Synchronizing the Transfer of Data
A Dynamic Memory Controller, the AM2964


In computers equipped with large memories, the job of ordering the dizzyingly complicated internal flow of data is a crucial one. Information, in the form of on and off signals, is constantly being shuttled about, at lightning speed, from ROM to RAM and from magnetic disks and tapes to RAM. In small systems, microprocessors usually supervise these data transfers, as well as perform their other duties.

  Microprocessors and dynamic RAMs are not perfectly compatible, however. Dynamic RAMs require constant refreshing, and most microprocessors are not equipped for this chore, which necessitates the inclusion of other chips. There's also a timing problem between the two types of ICs, since most memories are unable to inform the microprocessor of the precise instant at which they're ready to move on to another task, forcing engineers to slow the entire system down.

  To compensate for these drawbacks, engineers developed dynamic memory controllers. Such ICs have enormous supervisory capacity; the chip on the right, for example, can control up to eighty-eight 64-K dynamic RAMs. Memory controllers provide more precise timing of read and write operations, thereby speeding things up. They also provide regular refreshing of the RAMs to which they're attached and make it easier for microprocessors to address and retrieve data.

Resembling a fortress made of gold, the AM3964 can supervise dozens of dynamic RAMs. The fortress walls consist of aluminum, acting as a ground, the circuits inside the walls of bipolar transistors. This photo displays several AM2964 chips on a wafer, illuminated by brightly colored lights. Actual size: 0.143 x .0156 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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