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Performance optimization of VLSI interconnect layout
 Integration, the VLSI Journal
, 1996
"... This paper presents a comprehensive survey of existing techniques for interconnect optimization during the VLSI physical design process, with emphasis on recent studies on interconnect design and optimization for highperformance VLSI circuit design under the deep submicron fabrication technologies. ..."
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Cited by 117 (32 self)
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This paper presents a comprehensive survey of existing techniques for interconnect optimization during the VLSI physical design process, with emphasis on recent studies on interconnect design and optimization for highperformance VLSI circuit design under the deep submicron fabrication technologies. First, we present a number of interconnect delay models and driver/gate delay models of various degrees of accuracy and efficiency which are most useful to guide the circuit design and interconnect optimization process. Then, we classify the existing work on optimization of VLSI interconnect into the following three categories and discuss the results in each category in detail: (i) topology optimization for highperformance interconnects, including the algorithms for total wire length minimization, critical path length minimization, and delay minimization; (ii) device and interconnect sizing, including techniques for efficient driver, gate, and transistor sizing, optimal wire sizing, and simultaneous topology construction, buffer insertion, buffer and wire sizing; (iii) highperfbrmance clock routing, including abstract clock net topology generation and embedding, planar clock routing, buffer and wire sizing for clock nets, nontree clock routing, and clock schedule optimization. For each method, we discuss its effectiveness, its advantages and limitations, as well as its computational efficiency. We group the related techniques according to either their optimization techniques or optimization objectives so that the reader can easily compare the quality and efficiency of different solutions.
Zero Skew Clock Routing With Minimum Wirelength
 IEEE Transactions on Circuits and Systems
, 1992
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Clock Distribution Networks in Synchronous Digital Integrated Circuits
 Proc. IEEE
, 2001
"... this paper, bears separate focus. The paper is organized as follows. In Section II, an overview of the operation of a synchronous system is provided. In Section III, fundamental definitions and the timing characteristics of clock skew are discussed. The timing relationships between a local data path ..."
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Cited by 81 (6 self)
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this paper, bears separate focus. The paper is organized as follows. In Section II, an overview of the operation of a synchronous system is provided. In Section III, fundamental definitions and the timing characteristics of clock skew are discussed. The timing relationships between a local data path and the clock skew of that path are described in Section IV. The interplay among the aforementioned three subsystems making up a synchronous digital system is described in Section V; particularly, how the timing characteristics of the memory and logic elements constrain the design and synthesis of clock distribution networks. Different forms of clock distribution networks, such as buffered trees and Htrees, are discussed. The automated layout and synthesis of clock distribution networks are described in Section VI. Techniques for making clock distribution networks less sensitive to process parameter variations are discussed in Section VII. Localized scheduling of the clock delays is useful in optimizing the performance of highspeed synchronous circuits. The process for determining the optimal timing characteristics of a clock distribution network is reviewed in Section VIII. The application of clock distribution networks to highspeed circuits has existed for many years. The design of the clock distribution network of certain important VLSIbased systems has been described in the literature, and some examples of these circuits are described in Section IX. In an effort to provide some insight into future and evolving areas of research relevant to highperformance clock distribution networks, some potentially important topics for future research are discussed in Section X. Finally, a summary of this paper with some concluding remarks is provided in Section XI
ZeroSkew Clock Routing Trees With Minimum Wirelength," technical report UCLA CSD920012
, 1992
"... In the design of high performance VLSI systems, minimization of clock skew is an increasingly important objective. Additionally, wirelength of clock routing trees should be minimized in order to reduce system power requirements and deformation of the clock pulse at the synchronizing elements of t ..."
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Cited by 64 (14 self)
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In the design of high performance VLSI systems, minimization of clock skew is an increasingly important objective. Additionally, wirelength of clock routing trees should be minimized in order to reduce system power requirements and deformation of the clock pulse at the synchronizing elements of the system. In this paper, we present the DeferredMerge Embedding (DME) algorithm, which in linear time embeds any given connection topology into the Manhattan plane to create a clock tree with zero skew while minimizing total wirelength. Extensive experimental results show that the algorithm yields exact zero skew trees with 9% to 16 % wirelength reduction over previous constructions [5] [6]. The DME algorithm may be applied to either the Elmore or the linear delay model, and yields optimal total wirelength for linear delay. 1
ClusteringBased Optimization Algorithm in ZeroSkew Routings
 Proc. ACM/IEEE Design Automation Conf
, 1993
"... A zeroskew routing algorithm with clustering and improvement methods is proposed. This algorithm generates a zeroskew routing in O(n log n) time for n pins, and it is proven that the order of the total wire length is best possible. Our algorithm achieves 20% reduction of the total wire length and ..."
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Cited by 58 (2 self)
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A zeroskew routing algorithm with clustering and improvement methods is proposed. This algorithm generates a zeroskew routing in O(n log n) time for n pins, and it is proven that the order of the total wire length is best possible. Our algorithm achieves 20% reduction of the total wire length and 15%50% improvement of the delay time on benchmark data compared with the best known algorithm. 1 Department of Computer Science, Princeton University and C&C Systems Research Laboratories, NEC Corporation 1 Introduction Designing zeroskew routings with minimal delay time is one of the most crucial issues in current and future performancedriven layouts. In synchronous circuits, the clock skew t skew limits the clock period t c together with data path delay t d and other constant factors t const . The following equation formulates the clock period: t c = t skew + t d + t const : Therefore, in order to optimize the clock period, the clock skew needs to be minimized. In addition, in desi...
MatchingBased Methods for HighPerformance Clock Routing
 IEEE TRANS. ON CAD
, 1993
"... Minimizing clock skew is important in the design of high performance VLSI systems. We present a general clock routing scheme that achieves very small clock skews while still using a reasonable amount of wirelength. Our routing solution is based on the construction of a binary tree using geometric ma ..."
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Cited by 27 (7 self)
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Minimizing clock skew is important in the design of high performance VLSI systems. We present a general clock routing scheme that achieves very small clock skews while still using a reasonable amount of wirelength. Our routing solution is based on the construction of a binary tree using geometric matching. For cellbased designs, the total wirelength of our clock routing tree is on average within a constant factor of the wirelength in an optimal Steiner tree, and in the worst case is bounded by O(/x//  n) for n terminals arbitrarily distrib uted in the It x 12 grid. The bottomup construction readily extends to general cell layouts, where it also achieves essentially zero clock skew within reasonably bounded total wirelength. We have tested our algorithms on numerous random examples and also on layouts of industrial benchmark circuits. The results are promising: our clock routing yields nearzero average clock skew while using total wirelength competitive with previously known methods.
Automatic Synthesis of Gated Clocks for Power Reduction in Sequential Circuits
 IEEE Design and Test of Computers
, 1994
"... With the proliferation of portable devices and increasing levels of chip integration, reducing power consumption is becoming of paramount importance. We describe a technique to automatically synthesize gated clocks for finitestate machines (FSMs) to reduce power in the final implementation. This te ..."
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Cited by 25 (8 self)
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With the proliferation of portable devices and increasing levels of chip integration, reducing power consumption is becoming of paramount importance. We describe a technique to automatically synthesize gated clocks for finitestate machines (FSMs) to reduce power in the final implementation. This technique recognizes selfloops in the FSM (either from the state diagram or from a synchronous network) and uses the function described by the selfloops to gate the clock. The clock activation function is then used as don'tcare information to minimize the logic in the FSM for additional power savings. We applied these techniques to standard MCNC benchmarks and found an average reduction in power dissipation of 25%, at the cost of a 5% increase in area. 1 Introduction As portable devices proliferate and device sizes continue to shrink, allowing more devices to fit on a chip, power consumption has taken on increased importance. Much recent work has focused on accurate estimation of power co...
Simultaneous buffer and wire sizing for performance and power optimization
 in Proc. Int. Symp. on Low Power Electronics and Design
, 1996
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Delay Minimization for ZeroSkew Routing
 Proc. IEEE Intl. Conf. ComputerAided Design
, 1993
"... Delay minimization methods are proposed for zeroskew routings. A delaytime estimation formula is derived, which can be used as an objective function to be minimized in zeroskew routing algorithms. Moreover, the optimum wire width is formulated. Experimental results show that our methods with a cl ..."
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Cited by 22 (1 self)
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Delay minimization methods are proposed for zeroskew routings. A delaytime estimation formula is derived, which can be used as an objective function to be minimized in zeroskew routing algorithms. Moreover, the optimum wire width is formulated. Experimental results show that our methods with a clusteringbased algorithm achieve 50% reduction of the delay time on benchmark data with 3000 pins. 1 Department of Computer Science, Princeton University and C&C Systems Research Laboratories, NEC Corporation 1 Introduction With the increase of the clock rate in VLSI, the clocknet routing scheme plays more critical roles. In order to make the clock rate higher, at least two factors should be taken into account in clocknet routing. First, since the clock skew affects the clock period directly, exact zero skew is desired. Next, the delay time should be minimized in a clock net. Consider an example of singlephase clocking in Fig. 1. In CMOS design, the delay time is dominated by the rise/f...
ActivityDriven Clock Design
 IEEE TRANSACTIONS ON COMPUTERAIDED DESIGN OF INTEGRATED CIRCUITS AND SYSTEMS
, 2002
"... In this paper, we investigate reducing the power consumption of a synchronous digital system by minimizing the total power consumed by the clock signals. We construct activitydriven clock trees wherein sections of the clock tree are turned off by gating the clock signals. Since gating the clock sig ..."
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Cited by 22 (1 self)
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In this paper, we investigate reducing the power consumption of a synchronous digital system by minimizing the total power consumed by the clock signals. We construct activitydriven clock trees wherein sections of the clock tree are turned off by gating the clock signals. Since gating the clock signal implies that additional control signals and gates are needed, there exists a tradeoff between the amount of clock tree gating and the total power consumption of the clock tree. We exploit similarities in the switching activity of the clocked modules to reduce the number of clock gates. Assuming a given switching activity of the modules, we propose three novel activitydriven problems: a clock tree construction problem, a clock gate insertion problem, and a zeroskew clock gate insertion problem. The objective of these problems is to minimize system's power consumption by constructing an activitydriven clock tree. We propose an approximation algorithm based on recursive matching to solve the clock tree construction problem. We also propose an exact algorithm employing the dynamic programming paradigm to solve the gate insertion problems. Finally, we present experimental results that verify the effectiveness of our approach. This paper is a step in understanding how highlevel decisions (e.g., behavioral design) can affect a lowlevel design (e.g., clock design).