SWIFT: A Low-Power Network-On-Chip Implementing the Token Flow Control Router Architecture With Swing-Reduced Interconnects

A 64-bit, 8 × 8 mesh network-on-chip (NoC) is presented that uses both new architectural and circuit design techniques to improve on-chip network energy-efficiency, latency, and throughput. First, we propose token flow control, which enables bypassing of flit buffering in routers, thereby reducing buffer size and their power consumption. We also incorporate reduced-swing signaling in on-chip links and crossbars to minimize datapath interconnect energy. The 64-node NoC is experimentally validated with a 2 × 2 test chip in 90 nm, 1.2 V CMOS that incorporates traffic generators to emulate the traffic of the full network. Compared with a fully synthesized baseline 8 × 8 NoC architecture designed to meet the same peak throughput, the fabricated prototype reduces network latency by 20% under uniform random traffic, when both networks are run at their maximum operating frequencies. When operated at the same frequencies, the SWIFT NoC reduces network power by 38% and 25% at saturation and low loads, respectively

Low-swing signaling for energy efficient on-chip networks

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 65-69).On-chip networks have emerged as a scalable and high-bandwidth communication fabric in many-core processor chips. However, the energy consumption of these networks is becoming comparable to that of computation cores, making further scaling of core counts difficult. This thesis makes several contributions to low-swing signaling circuit design for the energy efficient on-chip networks in two separate projects: on-chip networks optimized for one-to-many multicasts and broadcasts, and link designs that allow on-chip networks to approach an ideal interconnection fabric. A low-swing crossbar switch, which is based on tri-state Reduced-Swing Drivers (RSDs), is presented for the first project. Measurement results of its test chip fabricated in 45nm SOI CMOS show that the tri-state RSD-based crossbar enables 55% power savings as compared to an equivalent full-swing crossbar and link. Also, the measurement results show that the proposed crossbar allows the broadcast-optimized on-chip networks using a single pipeline stage for physical data transmission to operate at 21% higher data rate, when compared with the full-swing networks. For the second project, two clockless low-swing repeaters, a Self-Resetting Logic Repeater (SRLR) and a Voltage-Locked Repeater (VLR), have been proposed and analyzed in simulation only. They both require no reference clock, differential signaling, and bias current. Such digital-intensive properties enable them to approach energy and delay performance of a point-to-point interconnect of variable lengths. Simulated in 45nm SOI CMOS, the 10mm SRLR featured with high energy efficiency consumes 338fJ/b at 5.4Gb/s/ch while the 10mm VLR raises its data rate up to 16.OGb/s/ch with 427fJ/b.by Sunghyun Park.S.M

SMART: A Single-Cycle Reconfigurable NoC for SoC Applications

As technology scales, SoCs are increasing in core counts, leading to the need for scalable NoCs to interconnect the multiple cores on the chip. Given aggressive SoC design targets, NoCs have to deliver low latency, high bandwidth, at low power and area overheads. In this paper, we propose Single-cycle Multi-hop Asynchronous Repeated Traversal (SMART) NoC, a NoC that reconfigures and tailors a generic mesh topology for SoC applications at runtime. The heart of our SMART NoC is a novel low-swing clockless repeated link circuit embedded within the router crossbars, that allows packets to potentially bypass all the way from source to destination core within a single clock cycle, without being latched at any intermediate router. Our clockless repeater link has been proven in silicon in 45nm SOI. Results show that at 2GHz, we can traverse 8mm within a single cycle, i.e. 8 hops with 1mm cores. We implement the SMART NoC to layout and show that SMART NoC gives 60% latency savings, and 2.2X power savings compared to a baseline mesh NoC.United States. Defense Advanced Research Projects Agency. The Ubiquitous High-Performance Computing Progra

Book Review

A Scholarly Review of “Error Control for Network-On-Chip Links” (Authors: Bo Fu and Paul Ampadu, 2012)Fu, B.; and Ampadu, P. 2012. Error Control for Network-On-Chip Links.Springer Science+Business Media, LLC, New York, NY, USA.Available: <http://dx.doi.org/10.1007/978-1-4419-9313-7>

Network-on-Chip

Limitations of bus-based interconnections related to scalability, latency, bandwidth, and power consumption for supporting the related huge number of on-chip resources result in a communication bottleneck. These challenges can be efficiently addressed with the implementation of a network-on-chip (NoC) system. This book gives a detailed analysis of various on-chip communication architectures and covers different areas of NoCs such as potentials, architecture, technical challenges, optimization, design explorations, and research directions. In addition, it discusses current and future trends that could make an impactful and meaningful contribution to the research and design of on-chip communications and NoC systems

Driving the Network-on-Chip Revolution to Remove the Interconnect Bottleneck in Nanoscale Multi-Processor Systems-on-Chip

The sustained demand for faster, more powerful chips has been met by the availability of chip manufacturing processes allowing for the integration of increasing numbers of computation units onto a single die. The resulting outcome, especially in the embedded domain, has often been called SYSTEM-ON-CHIP (SoC) or MULTI-PROCESSOR SYSTEM-ON-CHIP (MP-SoC). MPSoC design brings to the foreground a large number of challenges, one of the most prominent of which is the design of the chip interconnection. With a number of on-chip blocks presently ranging in the tens, and quickly approaching the hundreds, the novel issue of how to best provide on-chip communication resources is clearly felt. NETWORKS-ON-CHIPS (NoCs) are the most comprehensive and scalable answer to this design concern. By bringing large-scale networking concepts to the on-chip domain, they guarantee a structured answer to present and future communication requirements. The point-to-point connection and packet switching paradigms they involve are also of great help in minimizing wiring overhead and physical routing issues. However, as with any technology of recent inception, NoC design is still an evolving discipline. Several main areas of interest require deep investigation for NoCs to become viable solutions: • The design of the NoC architecture needs to strike the best tradeoff among performance, features and the tight area and power constraints of the onchip domain. • Simulation and verification infrastructure must be put in place to explore, validate and optimize the NoC performance. • NoCs offer a huge design space, thanks to their extreme customizability in terms of topology and architectural parameters. Design tools are needed to prune this space and pick the best solutions. • Even more so given their global, distributed nature, it is essential to evaluate the physical implementation of NoCs to evaluate their suitability for next-generation designs and their area and power costs. This dissertation performs a design space exploration of network-on-chip architectures, in order to point-out the trade-offs associated with the design of each individual network building blocks and with the design of network topology overall. The design space exploration is preceded by a comparative analysis of state-of-the-art interconnect fabrics with themselves and with early networkon- chip prototypes. The ultimate objective is to point out the key advantages that NoC realizations provide with respect to state-of-the-art communication infrastructures and to point out the challenges that lie ahead in order to make this new interconnect technology come true. Among these latter, technologyrelated challenges are emerging that call for dedicated design techniques at all levels of the design hierarchy. In particular, leakage power dissipation, containment of process variations and of their effects. The achievement of the above objectives was enabled by means of a NoC simulation environment for cycleaccurate modelling and simulation and by means of a back-end facility for the study of NoC physical implementation effects. Overall, all the results provided by this work have been validated on actual silicon layout

DDRNoC: Dual Data-Rate Network-on-Chip

This article introduces DDRNoC, an on-chip interconnection network capable of routing packets at Dual Data Rate. The cycle time of current 2D-mesh Network-on-Chip routers is limited by their control as opposed to the datapath (switch and link traversal), which exhibits significant slack. DDRNoC capitalizes on this observation, allowing two flits per cycle to share the same datapath. Thereby, DDRNoC achieves higher throughput than a Single Data Rate (SDR) network. Alternatively, using lower voltage circuits, the above slack can be exploited to reduce power consumption while matching the SDR network throughput. In addition, DDRNoC exhibits reduced clock distribution power, improving energy efficiency, as it needs a slower clock than a SDR network that routes packets at the same rate. Post place and route results in 28nm technology show that, compared to an iso-voltage (1.1V) SDR network, DDRNoC improves throughput proportionally to the SDR datapath slack. Moreover, a low-voltage (0.95V) DDRNoC implementation converts that slack to power reduction offering the 1.1V SDR throughput at a substantially lower energy cost

Energy efficient communication across on-chip wires in digital CMOS

For the past half century, CMOS process scaling has followed Moore's law, approximately doubling transistor density every 18 months. While locally routed wires have generally scaled with transistor size, longer wires have scaled at a slower rate and in some cases have grown larger as chip size and complexity have increased. Wires routed for non-local communication now consume a large and increasing portion of the power, thermal and area budgets in CMOS designs. Additionally, dynamic energy expended in driving locally routed wires has become comparable to that expended in logic. The goal of this research is to investigate methods of reducing the energy required for on-chip communication, primarily through the use of low-voltage swing signaling. A network-on-chip routing architecture is presented that uses complementary architectural and low-voltage swing signaling techniques to significantly improve the latency, throughput and power of an on-chip network. On-chip signaling circuits are presented that improve the suitability of low-voltage swing signaling for short wire lengths and reduced supply voltages. Finally, a procedure for improving the energy efficiency of wire loads in digital CMOS through the automated insertion of low-voltage swing signaling circuits is presented

High-speed, economical design implementation of transit network router

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.Includes bibliographical references (p. 88-90).by Kazuhiro Hara.M.S

FastTrackNoC: A DDR NoC with FastTrack Router Datapaths

This paper introduces FastTrackNoC, a Network-on-Chip router architecture that reduces latency by bypassing its switch traversal (ST) stage. FastTrackNoC adds a fast-track path between the head of a particular virtual channel (VC) buffer at each input port and the link of the opposite output. This allows non-turning flits to bypass ST when the required router resources are available. FastTrackNoC combines ST bypassing with existing techniques for reducing latency, namely, pipeline bypassing of control stages, precomputed routing and lookahead control signaling, to allow at best a flit to proceed directly to link traversal (LT). FastTrackNoC is applied to a Dual Data Rate (DDR) router in order to maximize throughput. Post place and route results in 28nm technology show that (i) compared to the current state of the art DDR NoCs, FastTrackNoC offers the same throughput and reduces average packet latency by 11-32% requiring up to 5% more power and (ii) compared to current state of the art Single Data Rate (SDR) NoCs, FastTrackNoC reduces packet latency by 9-40% and achieves 16-19% higher throughput with 5% higher power at the SDR NoC saturation point