Distributed Shared Mamory for NoC-based MPSoCs

As the number of cores and functionalities integrated in embedded devices increases, the amount of memory used on these devices also increases, justifying the development of memory architectures that present scalability, low energy consumption and low latency. Two factors impact the scalability of MPSoC systems: cache access latency and energy consumption. The distance of the processors to the cache banks and the cache coherence protocol influences both factors. This work proposes a physically distributed data L2 cache as the cache architecture for a NoC-based MPSoC, because it allows the concept of clustering, and the implementation of data migration algorithms to reducing cache access latency. Results show that the number of cycles required to execute a given application might reduce 23% with the appropriate number of L2 cache banks. Also, a directory-based cache coherence protocol was implemented, exploiting the NoC physical services to improve performance. Results show a reduction of 17% in the number of clock cycles and a reduction up to 86% (average reduction: 39%) in energy consumption for some cache transactions.