北航NoC课程(NoC的一个全面介绍).pdf

路径:源和desDnaDonHop之间的一组有序通道 Count:消息从源到desDnaDon的跳数 — 简单,有用的代理网络延迟 • 每个节点、链接会招致propagaDon延迟,即使在没有contenDonExisting On-Chip Network TopologiesNIAGARACELL EIBFB DIMM FB DINM FB DIMM FB DIMMMCUMCUMCUMCUccRINGCROSSBARXRORAU当兽自喜「到Figure aThe Cell Broadband Engi me(BE processor aditdure isessentially a muiompuer on a ip This ar hitacbure of heterogeneoushigh- perormance processin dements aa mommon intarontadt hasa stucan tat is designed br dishbuted outputingN旧U5y|/F( Ethernet+)Buffer switch CorePCleDD R2 Controller oDDR2 Controller 12X10Fower <95 Wx8(2.0 GHrSeDesGigabit EthernetPAleOXAUI DWide sIMDwide SIMDUART. J aIIIpL nCAG SAMESHe GeTRINGpCle 1D MESHPHY三Mu比t· ThreadedMulti-Thre adedSerDesWide SIMDWide SIMDDDR2 Controller 3DDR2 Controller 2LARABEETILERATRIPSAbstract metricsUse metrics to evaluate performance and costof topologyAlso influenced by routing/ flow controlAt this stageAssume ideal routing (perfect load balancing)Assume ideal flow control (no idle cycles on anychanneAbstract Metrics: DegreeSwitch Degree: number of links at a nodeProxy for estimating costHigher degree requires more links and port counts ateach routerBA22,3,4AAbstract Metrics: Hop CountPath: ordered set of channels between sourceand destinationHop Count: number of hops a message takesfrom source to destinationSimple, useful proxy for network latencyEvery node link incurs some propagation delay even whenno contentionMinimal hop count: smallest hop countconnecting two nodesHop CountNetwork diameter: large min hop count innetworkAverage minimum hop count: average acrossall src/dst pairsImplementation may incorporate non-minimalpathsIncreases average hop countHop CountBAMax= 4Max= 4Max=2AVg =2.21.771.33Uniform random trafficRing>Mesh> torusDerivations laterLatencyTime for packet to traverse networkStart: head arrives at input portEnd: tail departs output portLatency Head latency+ serialization latencySerialization latency: time for packet with Length L tocross channel with bandwidth b (l/b)Approximate with hop countOther design choices (routing, flow control) impactlatencyUnknown at this stageAbstract metrics: Maximum Channel loadEstimate max bandwidth the network cansupportMax bits per second (bps that can be injected byevery node before it saturatesSaturation: network cannot accept any more trafficDetermine the most congested linkFor given traffic patternWill limit overall network bandwidthEstimate load on this channel10