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the science of computing: virtual memoryIn the March-April issue, I described how a computer's storage system is organized as a hierarchy consisting of cache, main memory, and secondary memory (e.g., disk). The cache and main memory form a subsystem that functions like main memory but attains speeds approaching cache. What happens if a program and its data are too large for the main memory? This is not a frivolous question. Every generation of computer users has been frustrated by insufficient memory. A new line of computers may have sufficient storage for the computations of its predecessor, but new programs will soon exhaust its capacity. In 1960, a longrange planning committee at MIT dared to dream of a computer with 1 million words of main memory. In 1985, the Cray-2 was delivered with 256 million words. Computational physicists dream of computers with 1 billion words. Computer architects have done an outstanding job of enlarging main memories yet they have never kept up with demand. Only the shortsighted believe they can.
Document ID
Document Type
Reprint (Version printed in journal)
Denning, Peter J.
(NASA Ames Research Center Moffett Field, CA United States)
Date Acquired
August 19, 2013
Publication Date
June 1, 1986
Publication Information
Publication: American Scientist
Volume: 74
Issue: 3
Subject Category
Computer Programming and Software
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