Effective hardware-level thread synchronization for high performance and power efficiency in application specific multi-threaded embedded processors

Multi-threaded processors interleave the execution of several threads to reduce processor stalling time. Instruction cache misses usually account for a significant fraction of the overall stalling time due to frequent instruction fetches. Apart from incurring extended execution time (hence its direct impact on energy consumption), cache misses also lead to indirect power overheads and increased thread switching due to resulting main memory accesses. Therefore, minimizing instruction cache misses is important especially in designing application specific embedded processors that tend to be compact in size and consume low power. This paper aims to reduce instruction cache misses in a single pipeline processor for applications that offer embarrassing parallelism and enable the same code to be executed by a number of independent threads on different data sets. Such a design can be used as a building block processor for large multicomputer systems. We propose a micro-architectural level multithreading control design, which synchronizes the thread execution to allow cached instructions to be maximally reused by all threads. Our experiments show that our design not only increases the pipeline performance but also reduces the memory access frequency, hence effectively achieving high energy efficiency.