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With the advancement in CMOS technology and multiple processors on the chip, communication across these cores is managed by a network-on-chip (NoC). Power and performance of these NoC interconnects have become a significant factor.The authors aim to reduce the leakage power consumption of NoC buffers by the use of non-volatile spin transfer torque random access memory (STT-RAM)-based buffers. STT-RAM technology has the advantages of high density and low leakage but suffers from low endurance. This low endurance has an impact on the lifetime of the router on the whole due to unwanted write-variations governed by virtual channel (VC) allocation policies. Here various VC allocation policies that help the uniform distribution of the writes across the buffers are proposed. Iso-capacity and iso-area-based alternatives to replace SRAM buffers with STT-RAM buffers are also presented. Pure STT-RAM buffers, however, impact the network latency. To mitigate this, a hybrid variant of the proposed policies which uses alternative VCs made of SRAM technology in the case of heavy network traffic is proposed. Experimental evaluation of full system simulation shows that proposed policies reduce the write variation by 99% and improve lifetime by 3.2 times and 1093 times, respectively. Also a 55.5% gain in the energy delay product is obtained.

This chapter contains sections titled: Introduction Overview: Interconnect Architectures Bus: Basic Architecture SOC Standard Buses Analytic Bus Models Beyond the Bus: NOC with Switch Interconnects Some NOC Switch Examples Layered Architecture and Network Interface Unit Evaluating Interconnect Networks Conclusions Problem Set

High-speed metal interconnects play a significant role in the on-chip network system as the network performance largely depends on the behaviour of these interconnects. Variability in wire properties due to the surface roughness directly impacts the overall system performance. In this study, the authors evaluate the effects of interconnect surface roughness on deeply scaled on-chip interconnects (i.e. 22, 13, and 7 nm) in the context of the network on chip (NoC). The critical roughness parameters of interconnect in NoC are extracted by atomic force microscopy analysis of fabricated thin sheets of copper. Their analysis shows that in a 5 × 5 NoC with 25 cores on 2.5 mm × 2.5 mm die, rough interconnects can lead to a significant penalty on energy budget, bandwidth density, bit error rate, the figure of merit and total system throughput. Their analysis shows that this penalty is further increased by moving towards interconnection lines at advanced technology nodes. They simulate the bodytrack workload of PARSEC benchmark by using Tejas Simulator to show the penalty on latency and energy of the architecture due to the rough interconnects. Their study makes an attempt to qualitatively and quantitative highlight the impact of the interconnect surface roughness on the design of power-aware NoCs.

Networks-on-chip (NoC) is a communication paradigm that has emerged to tackle different on-chip challenges and satisfy different demands in terms of high performance and economical interconnect implementation. However, merely metal-based NoC pursuit offers limited scalability with the relentless technology scaling especially in global communications. To meet the scalability demand, this study proposes a new hybrid architecture empowered by both metal interconnect and Zenneck surface waves interconnects (SWIs). This architecture reduces the NoC average hop count between any communication pairs, which has been reflected as a better average delay and throughput. Furthermore, SWI enables more efficient power dissipation and faster cross the chip signal propagation. The authors’ initial results based on a cycle-accurate simulator demonstrate the effectiveness of the proposed system architecture, such as significant power reduction (23%), large average delay reduction (34%) and higher throughput (35%) compared with regular NoC. These results are achieved with negligible hardware and area overhead. This study explores promising potentials of SWI for future complex global communication.

The on chip communication intention is difficult due to communication necessities and the difficulty of the objective application is great. Notably, different communication areas might be actualized utilizing a similar chip range, for example, to enable various parallel applications to be stacked onto the device. So the system on chip (SoC) deployed in different topologies with different design parameters to achieve the requirements of the target application. Classical communication methods such as point to point, the bus is not an appropriate solution for future SoCs. That is difficult to send signals starting with one end then onto the next term of a clock cycle. Issues, for example, global wire delay and global synchronization will restrict us. With a specific end goal to beat these problems, architect utilizes new models, procedures, and tools from network design field and apply them to SoCs plan that prompts modern worldview called network on a chip. In this paper, the design components used and the operation of the proposed architecture is same with network on chip (NoC) approach. But it differs in the communication architecture with the introduction of the on-chip peripheral bus. And it differs from the NoC by its switching networks. We modified the switching system that is developed to support dynamically reconfigurable network. Due to this modification in the switching system restrict the area and the power use of the NoC.

Three-dimensional (3D) integration facilitates to integrate an increasing number of transistors into a single package. Despite improved performance and power efficiency, the integration of multiple dies in the same package potentially leads to new security threats, such as 3D hardware Trojans. This work conducts a thorough survey on hardware Trojans reported in 3D integrated circuits (ICs) and systems, and proposes a comprehensive characterization of 3D hardware Trojans. Several case studies are performed to validate the feasibility of 3D hardware Trojan implementation. Our experimental results indicate that 3D ICs indeed provide a better environment for inserting stealthy thermal-based Trojans than 2D ICs. Multiple FPGA boards are utilized to conceptually emulate the stacked 3D ICs that experience multi-tier hardware Trojans. The stealthiness and effectiveness of the proposed multi-tier Trojans are validated in our case studies. The emulation results further show that the existing current-based self-referencing Trojan detection method designed for 2D Trojans will result in a lower detection rate in 3D scenarios.

Biologically-inspired packet switched network on chip (NoC) based hardware spiking neural network (SNN) architectures have been proposed as an embedded computing platform for classification, estimation and control applications. Storage of large synaptic connectivity (SNN topology) information in SNNs require large distributed on-chip memory, which poses serious challenges for compact hardware implementation of such architectures. Based on the structured neural organisation observed in human brain, a modular neural networks (MNN) design strategy partitions complex application tasks into smaller subtasks executing on distinct neural network modules, and integrates intermediate outputs in higher level functions. This paper proposes a hardware modular neural tile (MNT) architecture that reduces the SNN topology memory requirement of NoC-based hardware SNNs by using a combination of fixed and configurable synaptic connections. The proposed MNT contains a 16:16 fully-connected feed-forward SNN structure and integrates in a mesh topology NoC communication infrastructure. The SNN topology memory requirement is 50 % of the monolithic NoC-based hardware SNN implementation. The paper also presents a lookup table based SNN topology memory allocation technique, which further increases the memory utilisation efficiency. Overall the area requirement of the architecture is reduced by an average of 66 % for practical SNN application topologies. The paper presents micro-architecture details of the proposed MNT and digital neuron circuit. The proposed architecture has been validated on a Xilinx Virtex-6 FPGA and synthesised using 65 nm low-power CMOS technology. The evolvable capability of the proposed MNT and its suitability for executing subtasks within a MNN execution architecture is demonstrated by successfully evolving benchmark SNN application tasks representing classification and non-linear control functions. The paper addresses hardware modular SNN design and implementation challenges and contributes to the development of a compact hardware modular SNN architecture suitable for embedded applications

This paper presents the result of experiments conducted in mesh networks on different routing algorithms, traffic generation schemes and switching schemes. A new network on chip (NoC) topology based on partial interconnection of mesh network is proposed and a routing algorithm supporting the proposed architecture is developed. The proposed architecture is similar to standard mesh networks, where four extra bidirectional channels are added which remove the congestion and hotspots compared to standard mesh networks with fewer channels. Significant improvement in delay (60% reduction) and throughput (60% increase) was observed using the proposed network and routing when compared with the ideal mesh networks. An increase in number of channels makes the switches expensive and could increase the area and power consumption. However, the proposed network can be useful in high speed applications with some compromise on area and power.

The advent of diminutive technology feature sizes has led to escalating transistor densities. Burgeoning transistor counts are casting a dark shadow on modern chip design: global interconnect delays are dominating gate delays and affecting overall system performance. Networks-on-Chip (NoC) are viewed as a viable solution to this problem because of their scalability and optimized electrical properties. However, on-chip routers are susceptible to another artifact of deep submicron technology, Process Variation (PV). PV is a consequence of manufacturing imperfections, which may lead to degraded performance and even erroneous behavior. In this work, we present the first comprehensive evaluation of NoC susceptibility to PV effects, and we propose an array of architectural improvements in the form of a new router design-called SturdiSwitch-to increase resiliency to these effects. Through extensive reengineering of critical components, SturdiSwitch provides increased immunity to PV while improving performance and increasing area and power efficiency.

Network-on-Chip (NoC) architectures and three-dimensional (3D) integrated circuits have been introduced as attractive options for overcoming the barriers in interconnect scaling while increasing the number of cores. Combining these two approaches is expected to yield better performance and higher scalability. This paper explores the possibility of combining these two techniques in a heterogeneity aware fashion. Specifically, on a heterogeneous 3D NoC architecture, we explore how different types of processors can be optimally placed to minimize data access costs. Moreover, we select the optimal set of links with optimal voltage levels. The experimental results indicate significant savings in energy consumption across a wide range of values of our major simulation parameters.