Exploring Cache Size and Core Count Tradeoffs in Systems with Reduced Memory Access Latency

One of the main challenges for computer architects is how to hide the high average memory access latency from the processor. In this context, Hybrid Memory Cubes (HMCs) can provide substantial energy and bandwidth improvements compared to traditional memory organizations. However, it is not clear how this reduced average memory access latency will impact the LLC. For applications with high cache miss ratios, the latency to search for the data inside the cache memory will impact negatively on the performance. The importance of this overhead depends on the memory access latency. In this paper, we present an evaluation of the L3 cache importance on a high performance processor using HMC also exploring chip area tradeoffs between the cache size and number of processor cores. We show that the high bandwidth provided by HMC memories can eliminate the need for L3 caches, removing hardware and making room for more processing power. Our evaluations show that performance increased 37% and the EDP improved 12% while maintaining the same original chip area in a wide range of parallel applications, when compared to DDR3 memories.