Interconnect Centric High Level Synthesis For Enhanced Layouts With Reduced Wirelength

Increased design complexity and time-to-market pressure in the integrated circuit (IC) industry call for a raised level of abstraction at which designs are specified. High-level synthesis is the process of generating register-transfer level (RTL) implementations from behavioral specifications, and it is the key enabler for a designing at a higher level beyond RTL. As IC manufacturing technology scales down to nanoscopic scale, the synthesis tools face a number of new challenges, including complexity, power and interconnect. In this dissertation, we propose a spectrum of new techniques in high-level synthesis to address the new challenges and to improve the quality of synthesis results. 1. Efficient and versatile scheduling engine using soft constraints. We present a scheduler that distinguishes soft constraints from hard constraints when exploring the design space, and identify a class of tractable scheduling problems with soft constraints. By exploiting the total unimodularity of the constraint matrix in an integer-linear programming formulation, we are able to solve the problem optimally in polynomial time. Compared to traditional methods, the proposed approach allows easier expression of various design intentions and optimization directions, and, at the same time, gives the scheduler freedom to make global trade-offs optimally. We show that this scheduling engine is flexible enough to support a variety of design considerations in high-level synthesis. 2. Behavior-level observability analysis and power optimization. We introduce the concept of behavior-level observability and its approximations in the context of high-level synthesis, and propose an efficient procedure to compute an approximated behavior-level observability of every operation in a dataflow graph. The algorithm exploits the observability-masking nature of some Boolean operations, as well as the select operation, and treats other operations as black boxes to allow efficient word-level analysis. The result is proven to be exact under the black-box abstraction. The behavior-level observability condition obtained by our analysis can be used to optimize operation gating in the scheduler. This leads to more opportunities in subsequent RTL synthesis for power reduction. To the best of our knowledge, this is the first time behavior-level observability analysis and optimization are performed in a systematic manner. 3. Layout-friendly high-level synthesis. We study a number of structural metrics for measuring the layout-friendliness of microarchitectures generated in high-level synthesis. For a piece of connected netlist, we introduce the spreading score to measures how far components can be spread from each other with bounded wire length in a graph embedding formulation. The intuition is that components in a layout-friendly netlist (e.g., a mesh) can spread over the layout region without introducing long interconnects. Spreading score can be approximated efficiently using a semidefinite programming relaxation. Another metric based on neighborhood population is also proposed. On a number of benchmarks, spreading score shows stronger bias in favor of interconnect structures that have shorter wire length after layout, compared to previous metrics based on cut size and total multiplexer inputs.

ABSTRACT: Aggressive scaling of nanoscale CMOS integrated circuits has created significant design challenges arising from increasing power densities, thermal concerns, and rising wire delays. The main contribution of this dissertation is the development of unified physical and high-level synthesis techniques for the design of ASICs with optimal chip temperatures and interconnect delays. Thermal issues are becoming a serious problem in high-performance VLSI circuits, adversely impacting performance, reliability, power consumption, and cooling costs. To address this, we present a temperature-aware behavioral synthesis (TABS) framework that combines power minimization with temperature-aware task scheduling, resource binding, and floorplanning. Compared to conventional low-power synthesis methods, our approach is effective in synthesizing circuits with lower chip temperatures and more uniform thermal distributions, with temperature reductions up to 23% when compared to low-power synthesis. We propose three techniques to address interconnect delays during high-level synthesis: (1) a simulated annealing (SA) based layout-aware high-level synthesis technique for 3-D integrated circuits, that tightly couples the synthesis tasks of resource binding and 3-D floorplanning. The proposed algorithm significantly outperforms a conventional synthesis flow that separates the binding and floorplanning steps, with improvements in the total wirelength by 29% and of the longest wirelength by 21%; (2) a floorplan-aware high-level synthesis technique that uses the topology of multi-terminal nets to improve interconnect delay estimates during resource binding. Experiments show that the use of accurate wire delay estimates during binding can reduce wire delays by as much as 49% in 70nm technology; (3) an iterative high-level design-space exploration engine that uses a priori stochastic wirelength estimates to guide binding decisions during high-level synthesis. The proposed approach offers a significant speed-up during design space exploration when compared to approaches that use traditional place-and-route to evaluate candidate solutions. Finally, we present a genetic algorithm (GA) based approach for high-level synthesis. We propose novel GA encoding, crossover, and mutation operators for the problem. The quality of the results generated by the GA are superior to those of several other techniques reported in the literature.

Three-Dimensional Integrated Circuit Design, Second Eition, expands the original with more than twice as much new content, adding the latest developments in circuit models, temperature considerations, power management, memory issues, and heterogeneous integration. 3-D IC experts Pavlidis, Savidis, and Friedman cover the full product development cycle throughout the book, emphasizing not only physical design, but also algorithms and system-level considerations to increase speed while conserving energy. A handy, comprehensive reference or a practical design guide, this book provides effective solutions to specific challenging problems concerning the design of three-dimensional integrated circuits. Expanded with new chapters and updates throughout based on the latest research in 3-D integration: Manufacturing techniques for 3-D ICs with TSVs Electrical modeling and closed-form expressions of through silicon vias Substrate noise coupling in heterogeneous 3-D ICs Design of 3-D ICs with inductive links Synchronization in 3-D ICs Variation effects on 3-D ICs Correlation of WID variations for intra-tier buffers and wires Offers practical guidance on designing 3-D heterogeneous systems Provides power delivery of 3-D ICs Demonstrates the use of 3-D ICs within heterogeneous systems that include a variety of materials, devices, processors, GPU-CPU integration, and more Provides experimental case studies in power delivery, synchronization, and thermal characterization

This self-contained book addresses the need for analysis, characterization, estimation, and optimization of the various forms of power dissipation in the presence of process variations of nano-CMOS technologies. The authors show very large-scale integration (VLSI) researchers and engineers how to minimize the different types of power consumption of digital circuits. The material deals primarily with high-level (architectural or behavioral) energy dissipation.

Research and development of logic synthesis and verification have matured considerably over the past two decades. Many commercial products are available, and they have been critical in harnessing advances in fabrication technology to produce today's plethora of electronic components. While this maturity is assuring, the advances in fabrication continue to seemingly present unwieldy challenges. Logic Synthesis and Verification provides a state-of-the-art view of logic synthesis and verification. It consists of fifteen chapters, each focusing on a distinct aspect. Each chapter presents key developments, outlines future challenges, and lists essential references. Two unique features of this book are technical strength and comprehensiveness. The book chapters are written by twenty-eight recognized leaders in the field and reviewed by equally qualified experts. The topics collectively span the field. Logic Synthesis and Verification fills a current gap in the existing CAD literature. Each chapter contains essential information to study a topic at a great depth, and to understand further developments in the field. The book is intended for seniors, graduate students, researchers, and developers of related Computer-Aided Design (CAD) tools. From the foreword: "The commercial success of logic synthesis and verification is due in large part to the ideas of many of the authors of this book. Their innovative work contributed to design automation tools that permanently changed the course of electronic design." by Aart J. de Geus, Chairman and CEO, Synopsys, Inc.

This volume provides a complete understanding of the fundamental causes of routing congestion in present-day and next-generation VLSI circuits, offers techniques for estimating and relieving congestion, and provides a critical analysis of the accuracy and effectiveness of these techniques. The book includes metrics and optimization techniques for routing congestion at various stages of the VLSI design flow. The subjects covered include an explanation of why the problem of congestion is important and how it will trend, plus definitions of metrics that are appropriate for measuring congestion, and descriptions of techniques for estimating and optimizing routing congestion issues in cell-/library-based VLSI circuits.

In the last few years, power dissipation has become an important design constraint, on par with performance, in the design of new computer systems. Whereas in the past, the primary job of the computer architect was to translate improvements in operating frequency and transistor count into performance, now power efficiency must be taken into account at every step of the design process. While for some time, architects have been successful in delivering 40% to 50% annual improvement in processor performance, costs that were previously brushed aside eventually caught up. The most critical of these costs is the inexorable increase in power dissipation and power density in processors. Power dissipation issues have catalyzed new topic areas in computer architecture, resulting in a substantial body of work on more power-efficient architectures. Power dissipation coupled with diminishing performance gains, was also the main cause for the switch from single-core to multi-core architectures and a slowdown in frequency increase. This book aims to document some of the most important architectural techniques that were invented, proposed, and applied to reduce both dynamic power and static power dissipation in processors and memory hierarchies. A significant number of techniques have been proposed for a wide range of situations and this book synthesizes those techniques by focusing on their common characteristics.