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Network-on-Chip & NoCSim. Praveen Bhojwani. Agenda. Brief introduction Development environment Design components. Introduction. Future SoC designs will be too complex and bus based communication will be incapable of providing the desired level performance
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Network-on-Chip & NoCSim Praveen Bhojwani
Agenda • Brief introduction • Development environment • Design components
Introduction • Future SoC designs will be too complex and bus based communication will be incapable of providing the desired level performance • On-chip networks address design issues
Design Issues • Regular network issues: topology • Energy efficient • Latency aware • Reliable communication • Testability • Interfacing • etc
NoCSim • Developed in SystemC • Interconnection network simulator • Features: • Topology: 2D torus • Source routing • Virtual channel based communication • Capable of providing QoS, via class based VC allocation • Configurable multi-source traffic sources
Features (contd…) • Given energy estimates for certain components, can provide Energy and Power estimates for communication in the network • Can be setup to provide end-to-end or hop-to-hop reliability
Components • InputChannel – input port • OutputChannel – output port • VCAllocator – VC allocator • CNIntf – core network interface • NWTile – composed of IC, OC and VCA • NoC – 2D torus network of NWTiles
Input Channel • Receives flits • Flits are flow digits • Packet is broken up into a number of flits • Each packet will have at least a HEAD and TAIL flit (if size==1, we have a HDT flit) • Classifies them into VCs
Input Channel (contd…) • Serves each VC in a round robin fashion • When serving HEAD flits (1st flit of a packet), requests VCAllocator for a VC at the next router • When providing QoS, it specifies the desired class • Forward flit to output channel in the desired direction • Also update credit information at the neighboring routers
Output Channel • Receives flits from Input Channels and sends them over the link to the next router • When providing reliability, it waits for ACK/NAK
VC Allocator • Receives VC requests for particular direction and class of service, returns free VC ids. • Accepts credit update information from Input Channels from all 5 directions
CNI – Core Network Interface • Acts as a traffic source and sink • Configured via configuration file • Active when system is setup for end-to-end reliability