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Exploiting the Behavior of Ready Instructions for Power Benefits in a Dynamically Scheduled Embedded Processor

Surendra, G and Banerjee, Subhasis and Nandy, SK (2004) Exploiting the Behavior of Ready Instructions for Power Benefits in a Dynamically Scheduled Embedded Processor. In: The 2004 47th Midwest Symposium on Circuits and Systems, MWSCAS '04, 25-28 July, Hiroshima,Japan, Vol.2, 441 -444.


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Many instructions in a dynamically scheduled superscalar processor spend a significant time in the instruction window (IW) waiting to be selected even though their dependencies are satisfied. These "delays" are due to resource constraints and the oldest first selection policy used in many processors that gives a higher priority to older ready instructions than younger ones. In this paper, we study the "delay" and criticality characteristics of instructions based on their readiness during dispatch. We observe that most ready-on-dispatch (ROD) instructions are non critical and show that 57% of these instructions spend more than 1 cycle in the IW. We analyze the impact of: (i) steering ROD instructions to slow low power functional units; and (ii) early issue of ROD instructions, on power and performance. We find that the "early issue and slow execution" of ROD instructions reduces power consumption by 4-12% while degrading performance by about 5%. On the other hand, "early issue normal execution" of ROD instructions results in 3.5% power savings with less than 1% performance loss. Further, we find that the above policies reduce the energy expended in executing wrong path instructions by about 2%.

Item Type: Conference Paper
Publisher: IEEE
Additional Information: �©1990 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.
Department/Centre: Division of Interdisciplinary Sciences > Supercomputer Education & Research Centre
Date Deposited: 12 Dec 2005
Last Modified: 19 Sep 2010 04:21
URI: http://eprints.iisc.ac.in/id/eprint/4388

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