Modified Hotspot Cache Architecture: A Low Energy Fast Cache for Embedded Processors

The cache memory plays a crucial role in the performance of any processor. The cache memory (SRAM), especially the on chip cache, is 3-4 times faster than the main memory (DRAM). It can vastly improve the processor performance and speed. Also the cache consumes much less energy than the main memory. That leads to a huge power saving which is very important for embedded applications. In today's processors, although the cache memory reduces the energy consumption of the processor, however the energy consumption in the on-chip cache account to almost 40% of the total energy consumption of the processor. In this paper, we propose a cache architecture, for the instruction cache, that is a modification of the hotspot architecture. Our proposed architecture consists of a small filter cache in parallel with the hotspot cache, between the L1 cache and the main memory. The small filter cache is to hold the code that was not captured by the hotspot cache. We also propose a prediction mechanism to steer the memory access to either the hotspot cache, the filter cache, or the L1 cache. Our design has both a faster access time and less energy consumption compared to both the filter cache and the hotspot cache architectures. We use Mibench and Mediabench benchmarks, together with the simplescalar simulator in order to evaluate the performance of our proposed architecture and compares it with the filter cache and the hotspot cache architectures. The simulation results show that our design outperforms both the filter cache and the hotspot cache in both the average memory access time and the energy consumption