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Proceedings 2001 International Conference on Parallel Architectures and Compilation Techniques (2001)
Barcelona, Spain
Sept. 8, 2001 to Sept. 12, 2001
ISBN: 0-7695-1363-8
pp: 0061
Huiyang Zhou , North Carolina State University
Mark C. Toburen , North Carolina State University
Eric Rotenberg , North Carolina State University
Thomas M. Conte , North Carolina State University
Abstract: Lower threshold voltages in deep sub-micron technologies cause more leakage current, increasing static power dissipation. This trend, combined with the trend of larger/more cache memories dominating die area, has prompted circuit designers to develop SRAM cells with low-leakage operating modes (e.g., sleep mode). Sleep mode reduces static power dissipation but data stored in a sleeping cell is unreliable or lost. So, at the architecture level, there is interest in exploiting sleep mode to reduce static power dissipation while maintaining high performance. Current approaches dynamically control the operating mode of large groups of cache lines or even individual cache lines. However, the performance monitoring mechanism that controls the percentage of sleep-mode lines, and identifies particular lines for sleep mode, is somewhat arbitrary. There is no way to know what the performance could be with all cache lines active, so arbitrary miss rate targets are set (perhaps on a per-benchmark basis using profile information) and the control mechanism tracks these targets. We propose applying sleep mode only to the data store and not the tag store. By keeping the entire tag store active, the hardware knows what the hypothetical miss rate would be if all data lines were active and the actual miss rate can be made to precisely track it. Simulations show an average of 73% of I-cache lines and 54% of D-cache lines are put in sleep mode with an average IPC impact of only 1.7%, for 64KB caches.

T. M. Conte, M. C. Toburen, H. Zhou and E. Rotenberg, "Adaptive Mode Control: A Static-Power-Efficient Cache Design," Proceedings 2001 International Conference on Parallel Architectures and Compilation Techniques(PACT), Barcelona, Spain, 2001, pp. 0061.
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