The cache hierarchy design in existing SMT and superscalar processors is optimized for latency, but not for bandwidth. The size of the L1 data cache did not scale over the past decade. Instead, larger unified L2 and L3 caches were introduced. This cache hierarchy has a high overhead due to the principle of containment, as all the cache blocks in the upper level caches are contained in the lower level cache. It also has a complex design to maintain cache coherence across all levels. Furthermore, this cache hierarchy is not suitable for future large-scale SMT processors, which will demand high bandwidth instruction and data caches with a large number of ports. This paper suggests the elimination of the cache hierarchy and replacing it with one-level caches for instruction and data. Multiple instruction caches can be used in parallel to scale the instruction fetch bandwidth and capacity. A one-level data cache can be split into a number of block-interleaved cache banks to serve multiple ...
Muhamed F. Mudawar, John R. Wani