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SYNTHESIS OF NETWORKS ON CHIPS FOR 3D SYSTEMS ON CHIPS. Srinivasan Murali, Ciprian Seiculescu, Luca Benini, Giovanni De Micheli. Presented by Puqing Wu. Context. 3D Chip Smaller Footprint Shorter Wires Delay Power Routing Congestion… NoC: helps reduce TVS (Through Silicon Vias).
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SYNTHESIS OF NETWORKS ON CHIPS FOR 3D SYSTEMS ON CHIPS Srinivasan Murali, Ciprian Seiculescu, Luca Benini, Giovanni De Micheli Presented by Puqing Wu
Context • 3D Chip • Smaller Footprint • Shorter Wires • Delay • Power • Routing Congestion… • NoC: helps reduce TVS (Through Silicon Vias) Copy from reference [2]
Contribution • Synthesis Approach (power focus) • NoC topology • NoC switches placement • Comparing to 3D optimized mesh -- 38% power reduction -- 25% latency reduction
Design Approach Copy from reference [1]
Input of Synthesis • Specification • Cores: name, size, position, layer assignment • Communication: bandwidth, latency, message type • Technology constraints: # TSV • Synthesis Procedure • power, area and timing models of Switch & TSV
Output of Synthesis • Topologies • Switches layer placement and position • Result of power, latency and area
Knobs: # TSV • Area • Place and Route Copy from reference [2]
Knobs: # Switches • # Switches = # Cores / Ports on switches • Fewer switches leads to longer links thus larger link power consumption (Congestion?) • More switches leads to more switching activities thus larger switch power • More ports on switches leads to lower frequency
Connecting Cores and Switches • # Switches per layer: • Min: # Cores /max # ports (frequency) • Max: # Cores / 1 Adapted from reference [1]
Connecting cores to switches • Questions: • How to group cores? • Different connectivity across layers? Adapted from reference [1]
Connecting Switches to Switches • Constraints for cost computation • max_ill – IFN -- When 2 to 3 links less then max_ill, assign soft_IFN • max_switch_size – IFN -- When exceeding switches connectivity, create indirect switches • Questions: • What is cost? • How to connect switches based on cost analysis?
Placing Switches • Solve Linear Program by minimize obj • Also remove overlaps, pipeline long links and add NI to cores Taken from reference [1]
Case Study: Triple Video Object Plane Decoder Copy from reference [1]
Case Study Copy from reference [1]
Case Study • Frequency (Lowest f results in Min Power) • Max switches size • Switch counts sweeping
Power Consumption Copy from reference [1]
Comparisons with Mesh • Testbench: D_36_4, D_36_6 and D_36_8; D_35_bot, D_65_pipe • 38% power saving • 24.5% latency reduction? Copy from reference [1]
Impact on ILL Constraint • A very tight constraint on the number of ILL significantly increase power and latency (Questions) Copy from reference [1]
Reference • [1] Srinivasan Murali , Ciprian Seiculescu , Luca Benini , Giovanni De Micheli, Synthesis of networks on chips for 3D systems on chips, Proceedings of the 2009 Asia and South Pacific Design Automation Conference, January 19-22, 2009, Yokohama, Japan. • [2] Dae Hyun Kim, Saibal Mukhopadhyay, and Sung Kyu Lim. Through-Silicon-Via Aware Interconnect Prediction and Optimization for 3D Stacked ics, SLIP’09, July 26–27, 2009, San Francisco, California, USA.