As VLSI technology moves into the Ultra-Deep Sub-Micron (UDSM) era, manufacturing variations, power supply noise and temperature variations greatly affect the performance and yield of VLSI circuits. Clock Distribution Network (CDN), which is one of the biggest and most important nets in any synchronous VLSI chip, is especially sensitive to these variations. To address this problem variability-aware analysis and optimization techniques for VLSI circuits are needed. In the first part of this thesis an analytical bound for the unwanted skew due to interconnect variation is established. Experimental results show that this bound is safer, tighter and computationally faster than existing approaches. This bound could be used in variation-aware clock tree synthesis. The second part of the thesis deals with optimizing a given clock tree to minimize the unwanted skew variations. Non-tree CDNs have been recognized as a promising approach to overcome the variation problem. We propose a novel non-tree CDN obtained by adding cross links in an existing clock tree. We analyze the effect of the link insertion on clock skew variability and propose link insertion schemes. The non-tree CDNs so obtained are shown to be highly tolerant to skew variability with very little increase in total wire-length. This can be used in applications such as ASIC design where a significant increase in the total wire-length is unacceptable.

Clock Distribution Network (CDN) is an important component of any synchronous logic circuit. The function of CDN is to deliver the clock signal to the clock sinks. Clock skew is defined as the difference in the arrival time of the clock signal at the clock sinks. Higher uncertainty in skew (due to PVT variations) degrades circuit performance by decreasing the maximum possible delay between any two sequential elements. Aggressive frequency scaling has also led to high power consumption especially in CDN. This dissertation addresses variation and power issues in the design of current and potential future CDN. The research detailed in this work presents algorithmic techniques for the following problems: (1) Variation tolerance in useful skew design, (2) Link insertion for buffered clock nets, (3) Methodology and algorithms for rotary clocking and (4) Clock mesh optimization for skew-power trade off. For clock trees this dissertation presents techniques to integrate the different aspects of clock tree synthesis (skew scheduling, abstract topology and layout embedding) into one framework- tolerance to variations. This research addresses the issues involved in inserting cross-links in a buffered clock tree and proposes design criteria to avoid the risk of short-circuit current. Rotary clocking is a promising new clocking scheme that consists of unterminated rings formed by differential transmission lines. Rotary clocking achieves reduction in power dissipation clock skew. This dissertation addresses the issues in adopting current CAD methodology to rotary clocks. Alternative methodology and corresponding algorithmic techniques are detailed. Clock mesh is a popular form of CDN used in high performance systems. The problem of simultaneous sizing and placement of mesh buffers in a clock mesh is addressed. The algorithms presented remove the edges from the clock mesh to trade off skew tolerance for low power. For clock trees as well as link insertion, our experiments indicate significant reduction in clock skew due to variations. For clock mesh, experimental results indicate 18.5% reduction in power with 1.3% delay penalty on a average. In summary, this dissertation details methodologies/algorithms that address two critical issues- variation and power dissipation in current and potential future CDN.

A number of fundamental topics in the field of high performance clock distribution networks is covered in this book. High Performance Clock Distribution Networks is composed of ten contributions from authors at academic and industrial institutions. Topically, these contributions can be grouped within three primary areas. The first topic area deals with exploiting the localized nature of clock skew. The second topic area deals with the implementation of these clock distribution networks, while the third topic area considers more long-range aspects of next-generation clock distribution networks. High Performance Clock Distribution Networks presents a number of interesting strategies for designing and building high performance clock distribution networks. Many aspects of the ideas presented in these contributions are being developed and applied today in next-generation high-performance microprocessors.

. . . ????????????????????????????????? ????????????? ????????????,????? ???? ??????????? ???????????????????? ???. THUCYDIDIS HISTORIAE IV:108 C. Hude ed. , Teubner, Lipsiae MCMXIII ???????????,????? ??,? ????????????????? ???????????????????? ?????? ?????? ?????? ??? ????????? ??? ?’ ?????????? ??’ ?????????? ? ??????? ??? ????????????? ???????. ???????????????????:108 ???????????? ?????????????????????? ?. ?????????????. ????????????,????? It being the fashion of men, what they wish to be true to admit even upon an ungrounded hope, and what they wish not, with a magistral kind of arguing to reject. Thucydides (the Peloponnesian War Part I), IV:108 Thomas Hobbes Trans. , Sir W. Molesworth ed. In The English Works of Thomas Hobbes of Malmesbury, Vol. VIII I have been introduced to clock design very early in my professional career when I was tapped right out of school to design and implement the clock generation and distribution of the Alpha 21364 microprocessor. Traditionally, Alpha processors - hibited highly innovative clocking systems, always worthy of ISSCC/JSSC publi- tions and for a while Alpha processors were leading the industry in terms of clock performance. I had huge shoes to ?ll. Obviously, I was overwhelmed, confused and highly con?dent that I would drag the entire project down.

Covers the statistical analysis and optimization issues arising due to increased process variations in current technologies. Comprises a valuable reference for statistical analysis and optimization techniques in current and future VLSI design for CAD-Tool developers and for researchers interested in starting work in this very active area of research. Written by author who lead much research in this area who provide novel ideas and approaches to handle the addressed issues

Recent years have seen rapid strides in the level of sophistication of VLSI circuits. On the performance front, there is a vital need for techniques to design fast, low-power chips with minimum area for increasingly complex systems, while on the economic side there is the vastly increased pressure of time-to-market. These pressures have made the use of CAD tools mandatory in designing complex systems. Timing Analysis and Optimization of Sequential Circuits describes CAD algorithms for analyzing and optimizing the timing behavior of sequential circuits with special reference to performance parameters such as power and area. A unified approach to performance analysis and optimization of sequential circuits is presented. The state of the art in timing analysis and optimization techniques is described for circuits using edge-triggered or level-sensitive memory elements. Specific emphasis is placed on two methods that are true sequential timing optimizations techniques: retiming and clock skew optimization. Timing Analysis and Optimization of Sequential Circuits covers the following topics: Algorithms for sequential timing analysis Fast algorithms for clock skew optimization and their applications Efficient techniques for retiming large sequential circuits Coupling sequential and combinational optimizations. Timing Analysis and Optimization of Sequential Circuits is written for graduate students, researchers and professionals in the area of CAD for VLSI and VLSI circuit design.

Clock mesh is widely used in microprocessor designs for achieving low clock skew and high process variation tolerance. Clock mesh optimization is a very diffcult problem to solve because it has a highly connected structure and requires accurate delay models which are computationally expensive. Existing methods on clock network optimization are either restricted to clock trees, which are easy to be separated into smaller problems, or naive heuristics based on crude delay models. A clock mesh sizing algorithm, which is aimed to minimize total mesh wire area with consideration of clock skew constraints, has been proposed in this research work. This algorithm is a systematic solution search through rigorous Sequential Quadratic Programming (SQP). The SQP is guided by an efficient adjoint sensitivity analysis which has near-SPICE(Simulation Program for Integrated Circuits Emphasis)-level accuracy and faster-than-SPICE speed. Experimental results on various benchmark circuits indicate that this algorithm leads to substantial wire area reduction while maintaining low clock skew in the clock mesh. The reduction in mesh area achieved is about 33%.

Improve the performance and reliability of synchronous digital integrated circuits with this anthology of key literature on the design and analysis of clock distribution networks for VLSI based computer and signal processing systems. Beginning with an extensive tutorial overview and bibliography, this all in one source offers substantive coverage of the most relevant issues related to the design of clock distribution networks for application to high performance synchronous design. Related topics include clock skew; automated layout of clock nets; distributed buffet and interconnect delays; clock distribution design of structured custom VLSI circuits; wafer scale integration; systolic arrays; globally asynchronous, locally synchronous systems; microwave issues; low power clocking techniques; process insensitive circuits; deterministic and probabilistic delay models; system timing specifications; clock distribution networks of well known circuits and future research in clock distribution networks. The material presented in Clock Distribution Networks in VLSI Circuits and Systems will be valuable to anyone with an interest in synchronous integrated circuits, computer design, or signal processing implementation issues.

"Education, arts and social sciences, natural and technical sciences in the United States and Canada".

A textbook on the fundamentals of VLSI design flow, covering the various stages of design implementation, verification, and testing.