Dynamic power management (DPM) is a design methodology for dynamically reconfiguring systems to provide the requested services and performance levels with a minimum number of active components or a minimum load on such components. DPM encompasses a set of techniques that achieves energy-efficient computation by selectively turning off (or reducing the performance of) system components when they are idle (or partially unexploited). In this paper, we survey several approaches to system-level dynamic power management. We first describe how systems employ power-manageable components and how the use of dynamic reconfiguration can impact the overall power consumption. We then analyze DPM implementation issues in electronic systems, and we survey recent initiatives in standardizing the hardware/software interface to enable software-controlled power management of hardware components.

A survey of design techniques for system-level dynamic power management : Special section on low-power electronics and design

Dynamic power management (DPM) is a design methodology for dynamically reconfiguring systems to provide the requested services and performance levels with a minimum number of active components or a minimum load on such components DPM encompasses a set of techniques that achieves energy-efficient computation by selectively turning off (or reducing the performance of) system components when they are idle (or partially unexploited) In this paper, we survey several approaches to system-level dynamic power management We first describe how systems employ power-manageable components and how the use of dynamic reconfiguration can impact the overall power consumption We then analyze DPM implementation issues in electronic systems, and we survey recent initiatives in standardizing the hardware/software interface to enable software-controlled power management of hardware components

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A survey of design techniques for system-level dynamic power management

An approach is presented for minimizing power consumption for digital systems implemented in CMOS which involves optimization at all levels of the design. This optimization includes the technology used to implement the digital circuits, the circuit style and topology, the architecture for implementing the circuits and at the highest level the algorithms that are being implemented. The most important technology consideration is the threshold voltage and its control which allows the reduction of supply voltage without significant impact on logic speed. Even further supply reductions can be made by the use of an architecture-based voltage scaling strategy, which uses parallelism and pipelining, to tradeoff silicon area and power reduction. Since energy is only consumed when capacitance is being switched power can be reduced by minimizing this capacitance through operation reduction choice of number representation, exploitation of signal correlations, resynchronization to minimize glitching, logic design, circuit design, and physical design. The low-power techniques that are presented have been applied to the design of a chipset for a portable multimedia terminal that supports pen input, speech I/O and full-motion video. The entire chipset that performs protocol conversion, synchronization, error correction, packetization, buffering, video decompression and D/A conversion operates from a 1.1 V supply and consumes less than 5 mW. >

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Minimizing power consumption in digital CMOS circuits

With the advent of portable and high-density microelectronic devices, the power dissipation of very large scale integrated (VLSI) circuits is becoming a critical concern. Accurate and efficient power estimation during the design phase is required in order to meet the power specifications without a costly redesign process. In this paper, we present a review of the power estimation techniques that have recently been proposed. >

A survey of power estimation techniques in VLSI circuits

Low power has emerged as a principal theme in today's electronics industry. The need for low power has caused a major paradigm shift in which power dissipation is as important as performance and area. This article presents an in-depth survey of CAD methodologies and techniques for designing low power digital CMOS circuits and systems and describes the many issues facing designers at architectural, logical, and physical levels of design abstraction. It reviews some of the techniques and tools that have been proposed to overcome these difficulties and outlines the future challenges that must be met to design low power, high performance systems.

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Power minimization in IC design: principles and applications

We present a new architecture for signed multiplication. The proposed architecture maintains the pure form of an array multiplier, exhibiting a much lower overhead than the Booth architecture. We propose a hybrid encoding for the architecture, which is a compromise between the minimal input dependency presented by binary encoding and the low switching characteristic of the Gray encoding. We have experimented using the Gray code for each group of m bits, thus potentially further reducing the switching activity both internally and at the inputs. The architecture is extended for radix-2/sup m/ encoding, which leads to a reduction of the number of partial lines, enabling a significant improvement in performance and power consumption. The flexibility of our architecture allows for the easy construction of multipliers for different values of m. The results we present show that the proposed architecture with radix-4 compares favorably in performance and power with the modified Booth multiplier.

A new architecture for 2's complement Gray encoded array multiplier

We propose an innovative method of encoding the states of finite state machines. Our approach consists of iteratively defining the code word, one bit at a time. In each iteration the input state machine is decomposed into two submachines, with the first submachine having only two states. One bit is therefore sufficient to encode this submachine and it can be assigned arbitrarily as the particular value it assumes for each state is of minimal influence in terms of the machine implementation. The process is repeated again having as input the second submachine, until all the bits are encoded. We provide experimental results which indicate that our method of iteratively defining one bit at a time can generally achieve superior results to existing sequential state assignment methods which try to solve large problems heuristically. >

Bitwise encoding of finite state machines

The last two decades have seen tremendous effort on the development of high-level algorithms for the multiplierless design of constant multiplications, i.e., using only addition, subtraction, and shift operations. Among the different types of constant multiplications, the multiplication of a constant matrix by an input vector, i.e., the constant matrix-vector multiplication (CMVM) operation, is the most general case and occurs in many digital signal processing (DSP) systems. This chapter addresses the problem of minimizing the number of addition and subtraction operations in a CMVM operation and introduces a hybrid algorithm that incorporates efficient techniques. This chapter also describes how the hybrid algorithm can be modified to handle a delay constraint. The experimental results on a comprehensive set of instances show the efficiency of the hybrid algorithms at both high-level and gate-level, in comparison to previously proposed methods.

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Multiplierless Design of Linear DSP Transforms

Power distribution systems provide the voltages and currents that devices in a circuit need to operate properly and silicon success requires its careful design and verification. However, problems like voltage drop, ground bounce and electromigration, which may cause chip failures, are worsening, as more devices, operating at higher frequencies, are placed closer together. Verification of this type of systems is usually done by simulation, a costly endeavor given the size of current grids, making the determination of the worst-case input setting a crucial task. Current methodologies are based on supposedly safe settings targeting either unrealistic simultaneous switching on all signals or heuristic accounts of the joint switching probability of nearby signals. In this paper we propose a methodology for computation of the worst-case stimuli for power grid analysis. This is accomplished by determining the input vector that maximizes the number of gates, in close proximity to each other, that can switch in a given time window. The addition of these temporal and spatial restrictions makes the solution of the underlying optimization problem feasible. Comparisons with existing alternatives show that only a fraction of the gates change in any given timing window, leading to a more robust and efficient verification methodology.

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Generating Worst-Case Stimuli for Accurate Power Grid Analysis

Since human beings have limited perceptual abilities, in many digital signal processing (DSP) applications, e.g., image and video processing, the outputs do not need to be computed accurately. Instead, their computation can be approximated so that the area, delay, and/or power dissipation of the design can be reduced. This paper presents an approximation algorithm, called aura, for the multiplierless design of the constant matrix vector multiplication (CMVM) which is a ubiquitous operation in DSP systems. aura aims to tune the constants such that the resulting matrix leads to a CMVM design which requires the fewest adders/subtractors, satisfying the given error constraints. This paper also introduces its modified version, called aura-dc, which can reduce the delay of the CMVM operation with a small increase in the number of adders/subtractors. Experimental results show that the proposed algorithms yield significant reductions in the number of adders/subtractors with respect to the original realizations without violating the error constraints, and consequently lead to CMVM designs with less area, delay, and power dissipation. Moreover, they can generate alternative CMVM designs under different error constraints, enabling a designer to choose the one that fits best in an application.

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José Monteiro

Papers

A new architecture for 2's complement Gray encoded array multiplier

Bitwise encoding of finite state machines

Multiplierless Design of Linear DSP Transforms

Generating Worst-Case Stimuli for Accurate Power Grid Analysis

A novel method for the approximation of multiplierless constant matrix vector multiplication