To take advantage of the full potential of ubiquitous computing, we will need systems which minimize powerconsumption. Weiser et al. and others have suggested that this may be accomplished by a CPU which dynamically changes speed and voltage, thereby saving energy by spreading run cycles into idle time. Here we continue this research, using a simulation to compare a number of policies for dynamic speed-setting. Our work clarifies a fundamental power vs. delay tradeoff, as well as the role of prediction and of smoothing in dynamic speed-setting policies. We conclude that success seemingly depends more on simple smoothing algorithms than on sophisticated prediction techniques, but defer to the replication of these results on future variable-speed systems. 1 Introduction Recent developments in ubiquitous computing make it likely that the future will see a proliferation of cordless computing devices. Clearly it will be advantageous for such devices to minimize power-consumption. The top p...

Increasing levels of microprocessor power dissipation call for new approaches at the architectural level that save energy by better matching of on-chip resources to application requirements. Selective cache ways provides the ability to disable a subset of the ways in a set associative cache during periods of modest cache activity, while the full cache may remain operational for more cache-intensive periods. Because this approach leverages the subarray partitioning that is already present for performance reasons, only minor changes to a conventional cache are required, and therefore, full-speed cache operation can be maintained. Furthermore, the tradeoff between performance and energy is flexible, and can be dynamically tailored to meet changing application and machine environmental conditions. We show that trading off a small performance degradation for energy savings can produce a significant reduction in cache energy dissipation using this approach. 1. Introduction Contin...

The reduction of energy consumption in microprocessors can be accomplished without impacting the peak performance through the use of dynamic voltage scaling (DVS). This approach varies the processor voltage under software control to meet dynamically varying performance requirements. This paper presents a foundation for the simulation and analysis of DVS algorithms. These algorithms are applied to a benchmark suite specifically targeted for PDA devices. 2.

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/tutorial of the power estimation techniques that have recently been proposed. Invited, IEEE Trans. on VLSI, Dec. 1994. 1. Introduction The continuing decrease in feature size and the corresponding increase in chip density and operating frequency have made power consumption a major concern in VLSI design [1, 2]. Modern microprocessors are indeed hot: the PowerPC chip from Motorola consumes 8.5 Watts, the Pentium chip from Intel consumes 16 Watts, and DEC's alpha chip consumes 30 Watts. Excessive power dissipation in integrated circuits not only discourages their use in a portable environment, but also causes overheating, which degr...

In this paper we investigate possible ways to improve the energy efficiency of a general purpose microprocessor. We show that the energy of a processor depends on its performance, so we chose the energy-delay product to compare different processors. To improve the energy-delay product we explore methods of reducing energy consumption that do not lead to performance loss (i.e., wasted energy), and explore methods to reduce delay by exploiting instruction level parallelism. We found that careful design reduced the energy dissipation by almost 25%. Pipelining can give approximately a 22 improvement in energydelay product. Superscalar issue, however, does not improve the energy-delay product any further since the overhead required offsets the gains in performance. Further improvements will be hard to come by since a large fraction of the energy (50--80%) is dissipated in the clock network and the on-chip memories. Thus, the efficiency of processors will depend more on the technology being ...

All rights reserved.

: The increasing demand for portable computing has elevated power consumption to be one of the most critical design parameters. A high-level synthesis system, HYPER-LP, is presented for minimizing power consumption in application specific datapath intensive CMOS circuits using a variety of architectural and computational transformations. The synthesis environment consists of high-level estimation of power consumption, a library of transformation primitives, and heuristic/probabilistic optimization search mechanisms for fast and efficient scanning of the design space. Examples with varying degree of computational complexity and structures are optimized and synthesized using the HYPER-LP system. The results indicate that more than an order of magnitude reduction in power can be achieved over current-day design methodologies while maintaining the system throughput; in some cases this can be accomplished while preserving or reducing the implementation area. 1.0 Introduction VLSI research a...

Abstruct- Technology trends and especially portable applications drive the quest for low-power VLSI design. Solutions that involve algorithmic, structural or physical transformations are sought. The focus is on developing low-power circuits without affecting too much the performance (area, latency, period). For CMOS circuits most power is dissipated as dynamic power for charging and discharging node capacitances. This is why many promising results in low-power design are obtained by minimizing the number of transitions inside the CMOS circuit. While it is generally accepted that because of the large capacitances involved much of the power dissipated by an IC is at the U0 little has been specifically done for decreasing the U0 power dissipation. We propose the Bus-Znvert method of coding the U0 which lowers the bus activity and thus decreases the U0 peak power dissipation by 50 % and the U0 average power dissipation by up to 25%. The method is general but applies best for dealing with buses. This is fortunate because buses are indeed most likely to have very large capacitances associated with them and consequently dissipate a lot of power.

Abstract—A microprocessor system is presented in which the supply voltage and clock frequency can be dynamically varied so that the system can deliver high throughput when required while significantly extending battery life during the low speed periods. The system consists of a dc-dc switching regulator, an ARM V4 microprocessor with a 16-kB cache, a bank of 64-kB SRAM ICs, and an I/O interface IC. The four custom chips were fabricated in a standard 0.6- m 3-metal CMOS process. The system can dynamically vary the supply voltage from 1.2 to 3.8 V in less than 70 s. This provides a throughput range of 6–85 MIPS with an energy consumption of 0.54–5.6 mW/MIP yielding an effective energy efficiency as high as 26 200 MIPS/W. Index Terms—Adaptive processor, energy efficient, low power, variable voltage. I.

This paper presents a system-level power management technique for energy saving of event-driven applications. We present a new predictive system-shutdown method to exploit sleep mode operations for energy saving. We use an exponential-average approach to predict the upcoming idle period. We introduce two mechanisms, prediction-miss correction and prewake-up, to improve the hit ratio and to reduce the delay overhead. Experiments on four different event-driven applications show that our proposed method achieves high hit ratios in a wide range of delay overheads, which results in a high degree of energy saving with low delay penalties.