Energy-Efficient Trace Reuse Cache for Embedded Processors

For an embedded processor, the efficiency of instruction delivery has attracted much attention since instruction cache accesses consume a great portion of the whole processor power dissipation. In this paper, we propose a memory structure called Trace Reuse (TR) Cache to serve as an alternative source for instruction delivery. Through an effective scheme to reuse the retired instructions from the pipeline back-end of a processor, the TR cache presents improvement both in performance and power efficiency. Experimental results show that a 2048-entry TR cache is able to provide 75% energy saving for an instruction cache of 16 kB, at the same time boost the IPC up to 21%. The scalability of the TR cache is also demonstrated with the estimated area usage and energy-delay product. The results of our evaluation indicate that the TR cache outperforms the traditional filter cache under all configurations of the reduced cache sizes. The TR cache exhibits strong tolerance to the IPC degradation induced by smaller instruction caches, thus makes it an ideal design option for the cases of trading cache size for better energy and area efficiency.