A Dual-Port Data Cache with Pseudo-Direct Mapping Function

Conventional on-chip (L1) data caches such as Direct-Mapped (DM) and 2-way Set-Associative Caches (SAC) have been widely used for high-performance uni (or multi)-processors. Unfortunately, these schemes suffer from high conflict misses since more than one address is mapped onto the same cache line. To reduce the conflict misses, much research has been done in developing different cache architectures such as 2-way Skewed-Associative cache (Skew cache). The 2-way Skew cache has a hardware complexity equivalent to that of 2-way SAC and has a miss-rate approaching that of 4-way SAC. However, the reduction in the miss-rate using a Skew cache is limited by the confined space available to disperse the conflicting accesses over small memory banks. This research proposes a dual-port data cache called Pseudo-Direct Cache (PDC) to minimize the conflict misses by dispersing addresses effectively over a single memory bank. Our simulation results show that PDC reduces those misses significantly compared to any conventional L1 caches and also achieves 10-15% lesser miss-rates than a 2-way Skew cache. SimpleScalar simulator is used for these simulations with SPEC95FP benchmark programs. Similar results were also seen over SPEC2000FP benchmark programs. Simulations over CACTI 3.0 were performed to evaluate the hardware implications of PDC over Skew cache. The simulation results show that the PDC has a simple hardware complexity similar to 2-way SAC and has 4-15% better AMAT compared to 2-way Skew cache. The PDC also reduces execution cycles significantly