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NoC design and optimization for Multi-core media processors

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CHAPTER 2. RELATED WORK 21<strong>for</strong> modelling case studies. Memory arrays, crossbars <strong>and</strong> arbiters <strong>for</strong>m the basic buildingblocks of all router models using this framework. Each of these building blocks havebeen modelled in detail to estimate switching capacitance. Switching activity is estimatedbased on traffic models assuming certain arrival rates at the input ports. The power numbers<strong>for</strong> both Alpha 21364 <strong>and</strong> Infinib<strong>and</strong> routers have been found to be matching thevendors’ estimates within a minor error margin.The high level power model presented in [86] to estimate power consumption in semiglobal<strong>and</strong> global interconnects considers switching power, power due to vias <strong>and</strong> repeaters.The high level model estimates switching power within an error of 6% with aspeedup of three-to-four orders of magnitude. Error in via power is under 3%. A segmentlength distribution model has been presented <strong>for</strong> cases where Rents rule is insufficient.The segment length distribution model has been validated by analyzing netlists of a setof complex <strong>design</strong>s.A wormhole router implementing a minimal adaptive routing algorithm with nearoptimal per<strong>for</strong>mance <strong>and</strong> feasible <strong>design</strong> complexity is proposed in [87]. The work alsoestimates the optimal size of FIFO in an adaptive router with fixed priority scheme. Theoptimal size of the FIFO is derived to be equal to the length of the packet in flits in thiswork.2.3.3 Complete <strong>NoC</strong> ExplorationSeveral frameworks have been proposed <strong>for</strong> complete <strong>NoC</strong> exploration[89][90][91]. Theseframeworks can be used as tools to derive a first cut analysis of effect of certain <strong>NoC</strong> configurationsat an early <strong>design</strong> phase. Such frameworks are the first steps <strong>for</strong> roadmappingfuture of on-chip networks.A technology aware <strong>NoC</strong> topology exploration tool has been presented in [89]. The<strong>NoC</strong> exploration is optimized <strong>for</strong> energy consumption of the entire SoC. The work characterizes2D Meshes <strong>and</strong> Torii along with higher dimensions, multiple hierarchies <strong>and</strong>express channels, <strong>for</strong> energy spent in the network. The work presents analytical modelsbased on <strong>NoC</strong> parameters such as average hop count <strong>and</strong> average flit traversal energy to

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