Cross-Layer Pathfinding for Off-Chip Interconnects

Off-chip interconnects for integrated circuits (ICs) today induce a diverse design space, spanning many different applications that require transmission of data at various bandwidths, latencies and link lengths. Off-chip interconnect design solutions are also variously sensitive to system performance, power and cost metrics, while also having a strong impact on these metrics. The costs associated with off-chip interconnects include die area, package (PKG) and printed circuit board (PCB) area, technology and bill of materials (BOM). Choices made regarding off-chip interconnects are fundamental to product definition, architecture, design implementation and technology enablement. Given their cross-layer impact, it is imperative that a cross-layer approach be employed to architect and analyze off-chip interconnects up front, so that a top-down design flow can comprehend the cross-layer impacts and correctly assess the system performance, power and cost tradeoffs for off-chip interconnects. Chip architects are not exposed to all the tradeoffs at the physical and circuit implementation or technology layers, and often lack the tools to accurately assess off-chip interconnects. Furthermore, the collaterals needed for a detailed analysis are often lacking when the chip is architected; these include circuit design and layout, PKG and PCB layout, and physical floorplan and implementation. To address the need for a framework that enables architects to assess the system-level impact of off-chip interconnects, this thesis presents power-area-timing (PAT) models for off-chip interconnects, optimization and planning tools with the appropriate abstraction using these PAT models, and die/PKG/PCB co-design methods that help expose the off-chip interconnect cross-layer metrics to the die/PKG/PCB design flows. Together, these models, tools and methods enable cross-layer optimization that allows for a top-down definition and exploration of the design space and helps converge on the correct off-chip interconnect implementation and technology choice. The tools presented cover off-chip memory interfaces for mobile and server products, silicon photonic interfaces, 2.5D silicon interposers and 3D through-silicon vias (TSVs). The goal of the cross-layer framework is to assess the key metrics of the interconnect (such as timing, latency, active/idle/sleep power, and area/cost) at an appropriate level of abstraction by being able to do this across layers of the design flow. In additional to signal interconnect, this thesis also explores the need for such cross-layer pathfinding for power distribution networks (PDN), where the system-on-chip (SoC) floorplan and pinmap must be optimized before the collateral layouts for PDN analysis are ready. Altogether, the developed cross-layer pathfinding methodology for off-chip interconnects enables more rapid and thorough exploration of a vast design space of off-chip parallel and serial links, inter-die and inter-chiplet links and silicon photonics. Such exploration will pave the way for off-chip interconnect technology enablement that is optimized for system needs. The basis of the framework can be extended to cover other interconnect technology as well, since it fundamentally relates to system-level metrics that are common to all off-chip interconnects

TSV placement optimization for liquid cooled 3D-ICs with emerging NVMs

Three dimensional integrated circuits (3D-ICs) are a promising solution to the performance bottleneck in planar integrated circuits. One of the salient features of 3D-ICs is their ability to integrate heterogeneous technologies such as emerging non-volatile memories (NVMs) in a single chip. However, thermal management in 3D-ICs is a significant challenge, owing to the high heat flux (~ 250 W/cm2). Several research groups have focused either on run-time or design-time mechanisms to reduce the heat flux and did not consider 3D-ICs with heterogeneous stacks. The goal of this work is to achieve a balanced thermal gradient in 3D-ICs, while reducing the peak temperatures. In this research, placement algorithms for design-time optimization and choice of appropriate cooling mechanisms for run-time modulation of temperature are proposed. Specifically, an architectural framework which introduce weight-based simulated annealing (WSA) algorithm for thermal-aware placement of through silicon vias (TSVs) with inter-tier liquid cooling is proposed for design-time. In addition, integrating a dedicated stack of emerging NVMs such as RRAM, PCRAM and STTRAM, a run-time simulation framework is developed to analyze the thermal and performance impact of these NVMs in 3D-MPSoCs with inter-tier liquid cooling. Experimental results of WSA algorithm implemented on MCNC91 and GSRC benchmarks demonstrate up to 11 K reduction in the average temperature across the 3D-IC chip. In addition, power density arrangement in WSA improved the uniformity by 5%. Furthermore, simulation results of PARSEC benchmarks with NVM L2 cache demonstrates a temperature reduction of 12.5 K (RRAM) compared to SRAM in 3D-ICs. Especially, RRAM has proved to be thermally efficient replacement for SRAM with 34% lower energy delay product (EDP) and 9.7 K average temperature reduction

Design, Extraction, and Optimization Tool Flows and Methodologies for Homogeneous and Heterogeneous Multi-Chip 2.5D Systems

Chip and packaging industries are making significant progress in 2.5D design as a result of increasing popularity of their application. In advanced high-density 2.5D packages, package redistribution layers become similar to chip Back-End-of-Line routing layers, and the gap between them scales down with pin density improvement. Chiplet-package interactions become significant and severely affect system performance and reliability. Moreover, 2.5D integration offers opportunities to apply novel design techniques. The traditional die-by-die design approach neither carefully considers these interactions nor fully exploits the cross-boundary design opportunities. This thesis presents chiplet-package cross-boundary design, extraction, analysis, and optimization tool flows and methodologies for high-density 2.5D packaging technologies. A holistic flow is presented that can capture all parasitics from chiplets and the package and improve system performance through iterative optimizations. Several design techniques are demonstrated for agile development and quick turn-around time. To validate the flow in silicon, a chip was taped out and studied in TSMC 65nm technology. As the holistic flow cannot handle heterogeneous technologies, in-context flows are presented. Three different flavors of the in-context flow are presented, which offer trade-offs between scalability and accuracy in heterogeneous 2.5D system designs. Inductance is an inseparable part of a package design. A holistic flow is presented that takes package inductance into account in timing analysis and optimization steps. Custom CAD tools are developed to make these flows compatible with the industry standard tools and the foundry model. To prove the effectiveness of the flows several design cases of an ARM Cortex-M0 are implemented for comparitive study

Méthodologies de conception ASIC pour des systèmes sur puce 3D hétérogènes à base de réseaux sur puce 3D

Dans cette thèse, nous étudions les architectures 3D NoC grâce à des implémentations de conception physiques en utilisant la technologie 3D réel mis en oeuvre dans l'industrie. Sur la base des listes d'interconnexions en déroute, nous procédons à l'analyse des performances d'évaluer le bénéfice de l'architecture 3D par rapport à sa mise en oeuvre 2D. Sur la base du flot de conception 3D proposé en se concentrant sur la vérification temporelle tirant parti de l'avantage du retard négligeable de la structure de microbilles pour les connexions verticales, nous avons mené techniques de partitionnement de NoC 3D basé sur l'architecture MPSoC y compris empilement homogène et hétérogène en utilisant Tezzaron 3D IC technlogy. Conception et mise en oeuvre de compromis dans les deux méthodes de partitionnement est étudiée pour avoir un meilleur aperçu sur l'architecture 3D de sorte qu'il peut être exploitée pour des performances optimales. En utilisant l'approche 3D homogène empilage, NoC topologies est explorée afin d'identifier la meilleure topologie entre la topologie 2D et 3D pour la mise en œuvre MPSoC 3D sous l'hypothèse que les chemins critiques est fondée sur les liens inter-routeur. Les explorations architecturales ont également examiné les différentes technologies de traitement. mettant en évidence l'effet de la technologie des procédés à la performance d'architecture 3D en particulier pour l'interconnexion dominant du design. En outre, nous avons effectué hétérogène 3D d'empilage pour la mise en oeuvre MPSoC avec l'approche GALS de style et présenté plusieurs analyses de conception physiques connexes concernant la conception 3D et la mise en œuvre MPSoC utilisant des outils de CAO 2D. Une analyse plus approfondie de l'effet microbilles pas à la performance de l'architecture 3D à l'aide face-à-face d'empilement est également signalé l'identification des problèmes et des limitations à prendre en considération pendant le processus de conception.In this thesis, we study the exploration 3D NoC architectures through physical design implementations using real 3D technology used in the industry. Based on the proposed 3D design flow focusing on timing verification by leveraging the benefit of negligible delay of microbumps structure for vertical connections, we have conducted partitioning techniques for 3D NoC-based MPSoC architecture including homogeneous and heterogeneous stacking using Tezzaron 3D IC technlogy. Design and implementation trade-off in both partitioning methods is investigated to have better insight about 3D architecture so that it can be exploited for optimal performance. Using homogeneous 3D stacking approach, NoC architectures are explored to identify the best topology between 2D and 3D topology for 3D MPSoC implementation. The architectural explorations have also considered different process technologies highlighting the wire delay effect to the 3D architecture performance especially for interconnect-dominated design. Additionally, we performed heterogeneous 3D stacking of NoC-based MPSoC implementation with GALS style approach and presented several physical designs related analyses regarding 3D MPSoC design and implementation using 2D EDA tools. Finally we conducted an exploration of 2D EDA tool on different 3D architecture to evaluate the impact of 2D EDA tools on the 3D architecture performance. Since there is no commercialize 3D design tool until now, the experiment is important on the basis that designing 3D architecture using 2D EDA tools does not have a strong and direct impact to the 3D architecture performance mainly because the tools is dedicated for 2D architecture design.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

ECO-CHIP: Estimation of Carbon Footprint of Chiplet-based Architectures for Sustainable VLSI

Decades of progress in energy-efficient and low-power design have successfully reduced the operational carbon footprint in the semiconductor industry. However, this has led to an increase in embodied emissions, encompassing carbon emissions arising from design, manufacturing, packaging, and other infrastructural activities. While existing research has developed tools to analyze embodied carbon at the computer architecture level for traditional monolithic systems, these tools do not apply to near-mainstream heterogeneous integration (HI) technologies. HI systems offer significant potential for sustainable computing by minimizing carbon emissions through two key strategies: ``reducing" computation by reusing pre-designed chiplet IP blocks and adopting hierarchical approaches to system design. The reuse of chiplets across multiple designs, even spanning multiple generations of integrated circuits (ICs), can substantially reduce embodied carbon emissions throughout the operational lifespan. This paper introduces a carbon analysis tool specifically designed to assess the potential of HI systems in facilitating greener VLSI system design and manufacturing approaches. The tool takes into account scaling, chiplet and packaging yields, design complexity, and even carbon overheads associated with advanced packaging techniques employed in heterogeneous systems. Experimental results demonstrate that HI can achieve a reduction of embodied carbon emissions up to 70\% compared to traditional large monolithic systems. These findings suggest that HI can pave the way for sustainable computing practices, contributing to a more environmentally conscious semiconductor industry.Comment: Under review at HPCA2

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

FPGA dynamic and partial reconfiguration : a survey of architectures, methods, and applications

Dynamic and partial reconfiguration are key differentiating capabilities of field programmable gate arrays (FPGAs). While they have been studied extensively in academic literature, they find limited use in deployed systems. We review FPGA reconfiguration, looking at architectures built for the purpose, and the properties of modern commercial architectures. We then investigate design flows, and identify the key challenges in making reconfigurable FPGA systems easier to design. Finally, we look at applications where reconfiguration has found use, as well as proposing new areas where this capability places FPGAs in a unique position for adoption

Doctor of Philosophy

dissertationPortable electronic devices will be limited to available energy of existing battery chemistries for the foreseeable future. However, system-on-chips (SoCs) used in these devices are under a demand to offer more functionality and increased battery life. A difficult problem in SoC design is providing energy-efficient communication between its components while maintaining the required performance. This dissertation introduces a novel energy-efficient network-on-chip (NoC) communication architecture. A NoC is used within complex SoCs due it its superior performance, energy usage, modularity, and scalability over traditional bus and point-to-point methods of connecting SoC components. This is the first academic research that combines asynchronous NoC circuits, a focus on energy-efficient design, and a software framework to customize a NoC for a particular SoC. Its key contribution is demonstrating that a simple, asynchronous NoC concept is a good match for low-power devices, and is a fruitful area for additional investigation. The proposed NoC is energy-efficient in several ways: simple switch and arbitration logic, low port radix, latch-based router buffering, a topology with the minimum number of 3-port routers, and the asynchronous advantages of zero dynamic power consumption while idle and the lack of a clock tree. The tool framework developed for this work uses novel methods to optimize the topology and router oorplan based on simulated annealing and force-directed movement. It studies link pipelining techniques that yield improved throughput in an energy-efficient manner. A simulator is automatically generated for each customized NoC, and its traffic generators use a self-similar message distribution, as opposed to Poisson, to better match application behavior. Compared to a conventional synchronous NoC, this design is superior by achieving comparable message latency with half the energy

Optimising and evaluating designs for reconfigurable hardware

Growing demand for computational performance, and the rising cost for chip design and manufacturing make reconfigurable hardware increasingly attractive for digital system implementation. Reconfigurable hardware, such as field-programmable gate arrays (FPGAs), can deliver performance through parallelism while also providing flexibility to enable application builders to reconfigure them. However, reconfigurable systems, particularly those involving run-time reconfiguration, are often developed in an ad-hoc manner. Such an approach usually results in low designer productivity and can lead to inefficient designs. This thesis covers three main achievements that address this situation. The first achievement is a model that captures design parameters of reconfigurable hardware and performance parameters of a given application domain. This model supports optimisations for several design metrics such as performance, area, and power consumption. The second achievement is a technique that enhances the relocatability of bitstreams for reconfigurable devices, taking into account heterogeneous resources. This method increases the flexibility of modules represented by these bitstreams while reducing configuration storage size and design compilation time. The third achievement is a technique to characterise the power consumption of FPGAs in different activity modes. This technique includes the evaluation of standby power and dedicated low-power modes, which are crucial in meeting the requirements for battery-based mobile devices

Heurísticas bioinspiradas para el problema de Floorplanning 3D térmico de dispositivos MPSoCs

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Informática, Departamento de Arquitectura de Computadores y Automática, leída el 20-06-2013Depto. de Arquitectura de Computadores y AutomáticaFac. de InformáticaTRUEunpu