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Multiprocessor system-on-chip (MP-SoC) platforms represent an emerging trend for embedded multimedia applications. To enable MP-SoC platforms, scalable communication-centric interconnect fabrics, such as networks-on-chip (NoCs), have been recently proposed. The shared memory represents one of the key elements in designing MP-SoCs to provide data exchange and synchronization support. This paper focuses on the energy/delay exploration of a distributed shared memory architecture, suitable for low-power on-chip multiprocessors based on NoC. A mechanism is proposed for the data allocation on the distributed shared memory space, dynamically managed by an on-chip hardware memory management unit (HwMMU). Moreover, the exploitation of the HwMMU primitives for the migration, replication, and compaction of shared data is discussed. Experimental results show the impact of different distributed shared memory configurations for a selected set of parallel benchmark applications from the power/-performance perspective. Furthermore, a case study for a graph exploration algorithm is discussed, accounting for the effects of the core mapping and the network topology on energy and performance at the system level.

The paper introduces a dynamic branch prediction scheme suitable for energy-aware Very Long Instruction Word (VLIW) processors. The proposed technique is based on a compiler hint mechanism to filter the accesses to the branch predictor blocks. We define a configurable hint instruction which anticipates some static information about the upcoming branch to reduce the hardware involved in the prediction, thus, the energy consumption. To analyze the effectiveness of the proposed low-power branch prediction scheme, we combined it with some well-known dynamic branch prediction techniques suitable for VLIW processors. The analyzed branch predictors are characterized by simple hardware implementations, matching the low-power characteristics of the target VLIW processors. Experimental results have been carried out on Lx, an industrial 4-issue VLIW architecture.