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Fault-Tolerant Network-Interface for Spatial Division Multiplexing Based Network-on-Chip By Anup Das.

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Presentation on theme: "Fault-Tolerant Network-Interface for Spatial Division Multiplexing Based Network-on-Chip By Anup Das."— Presentation transcript:

1 Fault-Tolerant Network-Interface for Spatial Division Multiplexing Based Network-on-Chip By Anup Das

2 2 Content 1.NoC Overview TDM-Based SDM-Based 2.Existing NI Architecture 3.New Area Optimized Architecture 4.Need for Fault-Tolerance 5.Fault-Tolerant NI Architectures Centralized Approach Distributed Approach 6.Results 7.Conclusion

3 Network-on-Chip Increasing Number of IPs/PEs per die Communication bottleneck with shared bus Need for a scalable alternative –Use of networking concepts –NoC proposed by Benini et al. 3 Switch NI IP NI IP Switch NI IP NI IP Switch NI IP Switch NI IP Switch

4 Network-on-Chip (contd.) Two techniques for communication –Time Division Multiplexing –Spatial Division Multiplexing 4 NI IP NI IP ABC TDM-based NoC Switch NI IP NI IP Switch A SDM-based NoC B C Switch

5 Network Interface Architecture N to 1 bit serializers – one for each outgoing wire Data Distributor to send data from output queues to one of the serializers Each distributor can send data to each of the serializers Not all the distributors are loaded all the time A single distributor can serve all the serializers 5

6 Network Interface Architecture 6 n to 1 Distributor 1 Queue 1 Queue 2 Queue 3 Distributor 2 Distributor 3 PE 32 Switch out[7] out[1] out[0]32

7 New Area Optimized NI Single distributor for all the serializers New component called “requester” added for interfacing with the queue 7 sIDqID , 001, , 100, , 111 At connection setup time – each serializer assigned to a queue Serializer requests for data which is then forwarded to corresponding queue Data from queues travels back to the requesting serializer 2 IDs introduced – serializer ID (sID) and queue ID (qID)

8 New Area Optimized NI 8 32 to 1 Distributor out[0] out[1] out[7] 32 to 1 Requester Queue 2 Queue 1 Queue 3 32 Switch PE 32

9 Need for Fault-Tolerance Transistor density on the rise Shrinking feature size Increasing number of faults manifesting post fabrication Yield Loss Need for fault-tolerance –IP/PE level –Interconnect Level Idea is to provide graceful degradation of performance in event of faults 9

10 NI Fault-Tolerance - Centralized Controller introduced between distributor and IP queues Changes data mapping dynamically when fault occurs with load balancing 10 n to 1 Distributor 1 Queue 1 Queue 2 Queue 3 Distributor 2 Distributor 3 PE 32 Switch out[0] Controller n to 1 out[1] n to 1 out[7] 32

11 Centralized NI Operation 11

12 NI Fault-Tolerance - Distributed Multiple Distributors and Requestors –each capable of fault recovery Two other IDs included – dID (distributor ID) and rID (requester ID) When forwarding request to requester, distributor forwards dID, sID and qID qID – used by requester to forward request to a queue dID – used by requester to send back data from the queue to the requesting distributor sID – used by the distributor to send data to the requesting serializer 12

13 Distributed NI Operation 13

14 Results

15 Experimental Setup NoC considered with 8 links per node Data packets of size 32 bits Centralized Design coded in VHDL Distributed Design in Verilog Synopsys Design Compiler for ASIC synthesis UMC 65nm Standard Cells Area and Power number from the synthesis tool Area number converted to gate count for comparison across technologies 15

16 Area Breakup 16 Centralized DesignDistributed Design ComponentsCentralized DesignDistributed Deign Distributor1.8K2.2K Requester-0.5K Controller1.5K- Serializer + Other5K4.5K Total (2 Distributors)10.1K9.9K

17 Area and Power Comparison 17

18 Increasing Fault-Tolerance 18

19 Throughput 19

20 Summary Distributed Design more area and power efficient but centralized design becomes more efficient with more distributors Single fault in the controller of centralized design will render it useless No single fault will affect distributed NI behavior Next Step – –Increase granularity of load balancing –Fault-tolerance of Serializer 20

21 Thank you


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