Reducing leakage power in peripheral circuits of L2 caches

Abstract

Leakage power has grown significantly and is a major challenge in microprocessor design. Leakage is the dominant power component in second-level (L2) caches. This paper presents two architectural techniques to utilize leakage reduction circuits in L2 caches. They primarily target the leakage in the peripheral circuitry of an L2 cache and as such have to be able to cope with longer delays. One technique exploits the fact that processor activity decreases significantly after an L2 cache miss occurs and saves power during L2 miss service time. Two algorithms, a static one and an adaptive one, are proposed for deciding when to apply this leakage reduction technique. Another technique attempts to keep the peripheral circuits in a lower-power state most of the time. The results for SPEC2K benchmarks show that the first technique can achieve a 18 to 22% reduction in L2 power consumption, on average (and up to 63%), depending on the decision algorithm. The second technique can save 25%, on average (and up to 80%). This comes with a negligible 1 to 2% performance impact, on average, depending on the technique used.