NDLI: Memory Bandwidth Limitations of Future Microprocessors

Content Provider	IEEE Xplore Digital Library
Author	Kagi, A. Goodman, J.R. Burger, D.
Copyright Year	1996
Abstract	This paper makes the case that pin bandwidth will be a critical consideration for future microprocessors. We show that many of the techniques used to tolerate growing memory latencies do so at the expense of increased bandwidth requirements. Using a decomposition of execution time, we show that for modern processors that employ aggressive memory latency tolerance techniques, wasted cycles due to insufficient bandwidth generally exceed those due to raw memory latencies. Given the importance of maximizing memory bandwidth, we calculate effective pin bandwidth, then estimate optimal effective pin bandwidth. We measure these quantities by determining the amount by which both caches and minimal-traffic caches filter accesses to the lower levels of the memory hierarchy. We see that there is a gap that can exceed two orders of magnitude between the total memory traffic generated by caches and the minimal-traffic caches---implying that the potential exists to increase effective pin bandwidth substantially. We decompose this traffic gap into four factors, and show they contribute quite differently to traffic reduction for different benchmarks. We conclude that, in the short term, pin bandwidth limitations will make more complex on-chip caches cost-effective. For example, flexible caches may allow individual applications to choose from a range of caching policies. In the long term, we predict that off-chip accesses will be so expensive that all system memory will reside on one or more processor chips.
Starting Page	78
Ending Page	78
File Size	1095621
Page Count	1
File Format	PDF
ISBN	0897917863
ISSN	10636897
DOI	10.1109/ISCA.1996.10002
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	1996-05-24
Access Restriction	Subscribed
Rights Holder	Association for Computing Machinery, Inc. (ACM)
Subject Keyword	Bandwidth Microprocessors Delay Permission Modems Filters Tellurium Random access memory Councils Sun fault-tolerance Scalable Shared Memory Multiprocessors backward error recovery coherence protocol
Content Type	Text
Resource Type	Article

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