片上网络拓朴优化:在离散平面上布局与布线

微系统芯片(System-on-Chip,SoC)发展到今天,集成密度指数增长和芯片面积的急剧膨胀使得全局连线的延时上升,可靠性下降,成为集成电路的设计瓶颈.片上网络(Network-on-Chip,NoC)是解决整个芯片上数据有效传输的结构之一,以片上网络为基础通信架构的微系统芯片称为片上网上系统芯片(System-on-Network-on-Chip,SoNoC).微系统芯片内通信模式兼有随机性和确定性,应该根据特定应用的通信特征设计片上网络.本文在确定SoNoC设计流程的基础上,根据SoNoC的通信特征,选择了合适的离散平面结构,对SoNoC的运算及控制等模块进行布局、对模块间的通信依赖关系进行布线,发展出FRoD(Floor-plan and Routing on Discrete Plane)算法,以自动生成片上网络的拓扑结构.该算法定义了离散平面的一般表示方法,并在四种典型的离散平面上使用不同规模的随机系统完成了系列实验.为了处理系统和网络之间的耦合关系,逐点分裂的布局算法可以逐步学习和适应系统的通信需求,同时优化系统的执行时间和通信能量,在运行随机任务流图的模拟系统上与随机布局结果相比可以节省30%左右的通信能量,20%左右的系统通信时间.串行、并行和串并混合的布线算法使用最短路径把通信关系分布在离散平面的通道上,使不同的通信关系尽量复用网络通道,与全连接网络相比可以节省10%到30%的面积代价.     

片上网络:新一代的片上系统结构

片上系统是使用共享或专用总线作为芯片的通信资源.由于这些总线具有一定的限制,因此扩展性较差,不能满足发展需求.在这种情况下,目前的片内互连结构将成为多核芯片的发展瓶颈.文章介绍了一种新型的片上体系结构(片上网络)来解决未来片上系统中总线所带来的不足.片上网络作为一种新的片上体系结构,可以解决片上系统设计中所带来的各种挑...     

片上网络容错路由算法研究

随着集成电路制造工艺的不断发展,集成在芯片上晶体管的数量也随之增多,已超过几十亿晶体管的规模,因此芯片上可以集成越来越多的IP核。随着芯片中IP核数量的增多,基于总线结构的片上系统(System-on-Chip,So C)已不能满足数据的通信要求,为了解决这个问题,片上网络(Network-on-Chip,No C)作为一种全新的互联结构被提出来。其核心是把网络设计的思想移植到芯片设计中,将片上资源互连起来,并将计算与通信分离。片上网络具有很好的空间可扩展性,采用的全局异步一局部同步的通信机制使并行通信效率更高。NOC带来了一种全新的片上通信方式,它的引入有利于提升可重用设计、解决通信瓶颈和全局同步等难题。本文在研究片上网络结构的基础上,针对片上网络多播通信的特点提出了一种多播容错路由算法。     

基于CPCI总线的多DSP红外多目标跟踪系统

根据红外多目标跟踪系统的设计需求,在硬件上设计了一个以两片ADSP-TS101DSP和一片FPGA为核心处理器、带CPCI总线接口的多处理器并行处理平台;在算法上采用了SB/MHT红外多目标跟踪算法.详细介绍了多处理器间的高速数据传输和同步通信设计方法,SB/MHT算法在双DSP上的移植实现,以及PLX9054 PCI桥接芯片的通信方式设计.     

一种面向应用的NoC容错路由算法

随着芯片集成度的不断提高,芯片制造工艺进入深亚微米级以后,片上将会出现更多难以预测与消除的故障类型。为了实现可靠的片上通信,应用容错机制与算法是一个重要的解决方案。本文提出一种面向应用的NoC容错路由算法,该算法在重负载时使用带有部分故障的链路并使流量在网络中均匀分布。同时给出了实现该算法需要的扩展后的路由器结构。仿真结果表明,所提出的路由算法与现有的路由算法相比,具有更好的时延性能。     

片上网络核心芯片的验证与测试

为提高芯片验证与测试的可靠性,针对片上网络核心芯片的结构特点,设计出一种基于宿主机/目标机通信模式的测试系统.重点描述了测试系统软硬件的设计与实现,并采用Stratix系列FPGA芯片进行原型测试和验证.实验结果表明,该系统可对芯片的复位、实现功能及稳定性进行全面测试,而且原理简单、操作方便、运行稳定,极大地提高了芯片...     

面向分布式网络数据的容错控制策略

随着多核处理器核心数量的增多,系统容量的扩大,在制造和运行过程中产生的故障将会增多,容错能力对于系统的可靠性将变得更加重要。而一个片上系统的正常工作,将会非常依赖于片上网络系统传输数据的可靠性。芯片的制造偏差和组件故障、多处理器系统芯片集成不规则IP以及动态的电源门控都将导致片上网络中出现不规则拓扑结构。片上网络应当具备可以重新配置网络路由方式并将数据传输路径绕过无法正常工作的位置。文中设计了一种用于路由计算的特定约束跳转配置方法,为了保证其健壮性,采用基于局部信息的通信方式,设计实现了分布式的路由器传输路径配置单元,并完成了该方法的算法实现。     

SoC设计中的片上通信体系结构研究

以超深亚微米工艺和IP核复用技术为支撑的系统芯片(SoC)技术,是目前超大规模集成电路和嵌入式电子产品设计的主流.SoC中各IP核之间的片上通信体系结构是SoC设计关键技术之一,同时对SoC的性能起着至关重要的作用.提出一种SoC中的混合片上通信体系结构,该体系结构将传统的共享总线与片上网络相结合,既保留了片上共享总线面积小的优点,又具有片上网络的并行通信的优点.此外,该混合片上通信还可以扩展到二维网络.     

片上网络技术发展现状及趋势浅析

半导体制造工艺的快速发展使得片上可以集成更大规模的硬件资源,片上网络的研究试图解决芯片中全局通信问题,使得从基于计算的设计转变为基于通信的设计,并实现可扩展的通信架构.本文回顾和总结了现有NoC研究工作,指出NoC是当前片上通信发展的主流趋势,并分析了当前NoC关键技术瓶颈,最后预测了多核的技术和产业发展趋势.     

面向通信能耗的3D NoC映射研究

对于传统的平面结构,三维片上网络(3D NoC)具有更好的集成度和性能,在单芯片内部可以集成更多的处理器核。3D NoC作为2D NoC的结构拓展,在性能提高和低功耗设计方面更具优越性,成为多核系统芯片结构的主流架构。映射就是应用某种算法寻找一种最优方案,将通信任务图的子任务分配到NoC的资源节点上,保证NoC的通信能耗最小。参照2D NoC的研究方法,提出了针对3D网格NoC的通信能耗模型,采用蚁群算法实现了面向通信能耗的NoC映射。实验结果表明,面向不同网络规模的3D网格NoC平台,蚁群映射同随机映射相比,通信能耗降低可以达23%～42%。     

A multiobjective scatter search algorithm for fault-tolerant NoC mapping optimisation

Mapping IP cores to an on-chip network is an important step in Network-on-Chip (NoC) design and affects the performance of NoC systems. A mapping optimisation algorithm and a fault-tolerant mechanism are proposed in this article. The fault-tolerant mechanism and the corresponding routing algorithm can recover NoC communication from switch failures, while preserving high performance. The mapping optimisation algorithm is based on scatter search (SS), which is an intelligent algorithm with a powerful combinatorial search ability. To meet the requests of the NoC mapping application, the standard SS is improved for multiple objective optimisation. This method helps to obtain high-performance mapping layouts. The proposed algorithm was implemented on the Embedded Systems Synthesis Benchmarks Suite (E3S). Experimental results show that this optimisation algorithm achieves low-power consumption, little communication time, balanced link load and high reliability, compared to particle swarm optimisation and genetic algorithm.     

Polaris: A System-Level Roadmapping Toolchain for On-Chip Interconnection Networks

Technology trends are driving parallel on-chip architectures in the form of multiprocessor systems-on-a-chip (MPSoCs) and chip multiprocessors (CMPs). In these systems, the increasing on-chip communication demand among the computation elements necessitates the use of scalable, high-bandwidth network-on-chip (NoC) fabrics instead of dedicated interconnects and shared buses. As transistor feature sizes are further miniaturized, more complicated NoC architectures become feasible that can support more demanding applications. Given the myriad emerging software-hardware combinations, for cost-effectiveness, a system designer critically needs to prune this widening NoC design-space to predict the interconnect fabric(s) that best balance(s) cost/performance, before the actual design process begins. This prompted us to develop Polaris, a system-level roadmapping toolchain for on-chip interconnection networks that helps designers predict the most suitable interconnection network design(s) tailored to their performance needs and power/silicon area constraints with respect to a range of applications that the system will run. Polaris explores the plethora of NoC designs based on projections of network traffic, architectures, and process characteristics. While Polaris's toolchain is extensible so new traffic, network designs, and technology processes can be added, the current version already incorporates 7872 NoC design points. Polaris is rapid, efficiently iterating over thousands of NoC design points, while maintaining high relative and absolute accuracies when validated against detailed NoC synthesis results.     

基于通讯的NoC设计

近年来，一种全新的集成电路体系结构——Network on Chip（NoC）已经成为徽电子学科研究的热点佃题之一，其核心思想是将计算机网络技术移植到芯片设计中来，从体系结构上彻底解决片上通讯的瓶颈问题。文章提出了一种基于通讯的NoC设计方法，通过监控和协调NoC的网络通讯来获得更好的性能．并总结了实现该设计方法所必须研究的关键技术。     

片上网络调度算法相关研究

随着半导体集成工艺的发展,单个芯片上集成的IP核数目急剧增加,片上网络(NoC)成为未来取代总线设计的新模式。调度算法作为NoC研究的关键问题之一,对整个网络的传输性能起着重要的作用。本文对片上网络虚信道路由器调度算法的相关研究进展进行了总结,首先从路由器结构特点出发,介绍了几种典型的NoC仲裁器和调度器实例,总结相应的算法设计思想。再对NoC常用路由器调度算法进行了分类介绍,详细分析了各种调度算法的相关特性。最后,探讨了NoC路由器调度算法的研究方向。     

A Simple BCH Decoder for NoC Interconnects and SoC Buses

Network on a chip (NoC) uses packet-switched network to implement interconnections in System on chip (SoC). In SoC design, performance and energy efficiency are respectively the first and second priorities, and optimal on-chip communication should decrease the power consumption and area overhead. In this work, a simplified BCH codec is proposed for reliable communication in NoC and SoC. It performs BCH error corrections without Berlekamp's algorithm, only using reduced syndrome bits to determine error patterns. The error locations can be found by looking up tables, by which the possible errors are directly corrected. Only one matrix product and one ROM access are required in the BCH decoder. The proposed (20, 8, 2) and (31, 16, 3) decoders in the paper can be easily applied for error corrections of interconnects and buses for NoC and SoC. It is also beneficial to correct data lines without length definition and controllines without storage.     

3DNoC关键通信部件容错方法研究综述

三维片上网络通过硅通孔（Through Silicon Via,TSV）将多层芯片进行堆叠,具有集成密度大,通信效率高等特点,是片上多核系统的主流通信架构。然而,工艺偏差及物理缺陷所引发的错误和TSV良率较低等因素,使得三维片上网络面临严重的故障问题。为保证通信效率,对三维片上网络关键通信部件进行容错设计必不可少。本文针对三维片上网络关键通信部件———路由器和TSV的故障和容错相关问题,从容错必要性、国内外研究现状、未来的研究方向和关键问题、以及拟提出的相关解决方案四个方面,展开深入探讨。为提高片上网络可靠性、保证系统高效通信提供一体化的解决方案。     

Applying CDMA Technique to Network-on-Chip

The issues of applying the code-division multiple access (CDMA) technique to an on-chip packet switched communication network are discussed in this paper. A packet switched network-on-chip (NoC) that applies the CDMA technique is realized in register-transfer level (RTL) using VHDL. The realized CDMA NoC supports the globally-asynchronous locally-synchronous (GALS) communication scheme by applying both synchronous and asynchronous designs. In a packet switched NoC, which applies a point-to-point connection scheme, e.g., a ring topology NoC, data transfer latency varies largely if the packets are transferred to different destinations or to the same destination through different routes in the network. The CDMA NoC can eliminate the data transfer latency variations by sharing the data communication media among multiple users concurrently. A six-node GALS CDMA on-chip network is modeled and simulated. The characteristics of the CDMA NoC are examined by comparing them with the characteristics of an on-chip bidirectional ring topology network. The simulation results reveal that the data transfer latency in the CDMA NoC is a constant value for a certain length of packet and is equivalent to the best case data transfer latency in the bidirectional ring network when data path width is set to 32 bits.     

接口标记容错路由算法

随着片上系统(SoC)集成度的不断提高,IP核之间的通信故障成为亟待解决的问题,片上网络(NoC)是解决SoC通信问题的有效途径。容错路由算法是NoC设计中的关键技术,对NoC的通信效率有重要影响。在Valiant随机路由算法和源路由算法的基础上,提出了一种接口标记容错路由算法。该算法吸取了Valiant随机路由算法能平衡网络负载、降低拥塞概率的优良性能与源路由算法中路径不需要计算与查找的特点,减小了传输时延,提高了路由器的利用率。     

Low-cost and low-power unidirectional torus network-on-chip with corner buffer power-gating

Network-on-chip (NoC) is one of critical communication architectures for the scaling of future many-core processors. The challenge for on-chip network is reducing design complexity to save both area and power while providing high performance such as low latency and high throughput. Especially, with increase of network size, both design complexity and power consumption have become the bottlenecks preventing proper network scaling. Moreover, as technology continuously scales down, leakage power takes up a larger fraction of total NoC power. It is increasingly important for a power-efficient NoC design to reduce the increasing leakage power. Power-gating, as a representative low-power technique, can be applied to an on-chip network for mitigating leakage power. In this paper, we propose a low-cost and low-power router architecture for the unidirectional torus network, and adopt an improved corner buffer structure for the inoffensive power-gating, which has minimal impact on network performance. Besides, an explicit starvation avoidance mechanism is introduced to guarantee injection fairness while decreasing its negative impact on network throughput. Simulation results with synthetic traffic show that our design can improve network throughput by 11.3% on average and achieve significant power-saving in low- and medium-load regions. In the SPLASH-2 workload simulation, our design can save on average 27.2% of total power compared to the baseline, and decrease 42.8% average latency compared to the baseline with power-gating.     

An interconnection architecture for network-on-chip systems

Network on Chip (NoC) is a discipline research path that primarily addresses the global communication in System on Chip (SoC). It is inspired and uses the same routing and switching techniques needed in multi-computer networks. Current shared-bus based on-chip communication architectures generally have limited scalability due to the nature of the buses especially when complex on-chip communication SoC is needed. The main goal is to have a dedicated communication infrastructure in the system that can scale up while minimizing the area and power. The selected topology of the components interconnects plays prime rule in the performance of NoC architecture as well as routing and switching techniques that can be used. In this paper, we introduce a new NoC architecture by adapting a recursive topology structure. An experimental study is performed to compare this structure with basic NoC topologies represented by 2D mesh and Spidergon. The analysis illustrates the main features of this topology and its unique benefits. The simulation results show that recursive network outperforms 2D mesh and Spidergon in main performance metrics.