7. Concluding remarks

Cache memories have been around and in use since the late 1960s. Since the mid-1990s, the growing gap between processor performance, and in particular cycle times, and DRAM performance has led to increasingly complex cache hierarchies. All processors of the 2010s have two or three cache levels. When these processors are multi-core, the coherence aspect of multi-processor caches is added. We have looked at the hardware aspects of cache hierarchies and software optimizations to take account of cache characteristics.