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Summary: Simultaneous Multithreading: Maximizing OnChip Parallelism
Dean M. Tullsen, Susan J. Eggers, and Henry M. Levy
Department of Computer Science and Engineering
University of Washington
Seattle, WA 98195
Abstract
This paper examines simultaneous multithreading, a technique per
mitting several independent threads to issue instructions to a su
perscalar's multiple functional units in a single cycle. We present
several models of simultaneous multithreading and compare them
with alternative organizations: a wide superscalar, a finegrain mul
tithreaded processor, and singlechip, multipleissue multiprocess
ing architectures. Our results show that both (singlethreaded) su
perscalar and finegrain multithreaded architectures are limited in
their ability to utilize the resources of a wideissue processor. Si
multaneous multithreading has the potential to achieve 4 times the
throughput of a superscalar, and double that of finegrain multi
threading. We evaluate several cache configurations made possible
by this type of organization and evaluate tradeoffs between them.
We also show that simultaneous multithreading is an attractive alter
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