Normally-Off Computing

herausgegeben von: Takashi Nakada, Hiroshi Nakamura

Verlag: Springer Japan

Enthalten in: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik" , Springer Professional "Wirtschaft"

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Über dieses Buch

As a step toward ultimate low-power computing, this book introduces normally-off computing, which involves inactive components of computer systems being aggressively powered off with the help of new non-volatile memories (NVMs). Because the energy consumption of modern information devices strongly depends on both hardware and software, co-design and co-optimization of hardware and software are indispensable to improve energy efficiency.

The book discusses various topics including (1) details of low-power technologies including power gating, (2) characteristics of several new-generation NVMs, (3) normally-off computing architecture, (4) important technologies for implementing normally-off computing, (5) three practical implementations: healthcare, mobile information devices, and sensor network systems for smart city applications, and (6) related research and development.

Bridging computing methodology and emerging memory devices, the book is designed for both hardware and software designers, engineers, and developers as comprehensive material for understanding normally-off computing.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Introduction

Abstract

Improvement of energy efficiency is indispensable for computer systems in our rapidly evolving information society. To reduce energy consumption without performance degradation, aggressive and careful power management is necessary. Simple power gating cannot fully take the chances of power reduction since volatile memories lose data when power supply is off. However, with new non-volatile memories (NVMs), a synergetic effect for drastic energy reduction is highly expected. Normally-off computing is a way of computing where inactive components of computer systems are aggressively powered off with the help of new NVMs. As a result, high attention has been paid to normally-off computing using these NVMs and cooperation among algorithm, OS, compiler, architecture, circuit and device.

Takashi Nakada, Hiroshi Nakamura

Chapter 2. Low-Power Circuit Technologies

Abstract

In this chapter, basic low power techniques are explained including DVFS and other power management such as power gating. Discussion on energy overhead of these techniques is given to understand the limitation on temporal granularity. Normally-off computing tries to apply fine-grain power management with the help of non-volatile memory. Thus, access time and read/write energy of non-volatile memory are also discussed to reveal the condition to reduce energy from the view point of temporal granularity of memory accesses.

Takashi Nakada

Chapter 3. Non-volatile Memories

Abstract

This chapter describes the basic properties of various computer memories. Historical evolution of the roles of non-volatile functionalities in computer architecture is discussed to explain recent rejuvenating interest in new non-volatile memory technologies. Next, required properties for memories, such as scalability, access speed, power consumption, are discussed referring to those of current main-stream memories, i.e., dynamic random access memory (DRAM), static RAM, and NAND flash memory. Then, histories, working principles, and properties of spin-transfer torque magnetoresistive RAM, resistive RAM, phase change RAM, ferroelectric RAM, and NOR flash memory are described. Finally, possible positioning of these various non-volatile memories in future computer architecture are discussed.

Koji Ando, Shinobu Fujita, Masanori Hayashikoshi, Yoshikazu Fujimori

Chapter 4. Normally-Off Computing

Abstract

Normally-off computing is based on synergetic effect of aggressive power gating and non-volatile memory. To maximize opportunity of power reduction, as frequent as possible power management is necessary but too frequent state transition increases overhead energy. To manage this tradeoff, Break Even Time is introduced. If BET is small, there is more opportunity of power reduction. Therefore, new device that has small BET is desired. In addition to this, architectural technologies are also important to reduce effective BET by combining multiple devices that has different characteristics. Finally, using such heterogeneous devices, dynamic behavior is managed by software and energy consumption is minimized. To realize normally-off computing, hardware/software co-design and co-optimization are required. This is a key for not only system designers, but also hardware engineers and software developers.

Takashi Nakada, Hiroshi Nakamura

Chapter 5. Technologies for Realizing Normally-Off Computing

Abstract

Normally-off computing relies on device technologies, architectural and activity management technologies. To realize normally-off computing systems, details of each technology should be studied. Device technologies provide component that has as small BET as possible by minimizing energy overhead. Architectural technologies combined several devices that have different characteristics and realize flexible components that can adapt to a wide variety of applications. Activity management is done by software such as task scheduling. Based on these knowledges, normally-off computing system is realized.

Takashi Nakada, Shinobu Fujita, Masanori Hayashikoshi, Yoshikazu Fujimori, Hiroshi Nakamura

Chapter 6. Research and Development of Normally-Off Computing—NEDO Project

Abstract

Based on normally-off computing design methodology, we developed three practical systems that introduced normally-off computing. These systems are healthcare, mobile information device and sensor node for social infrastructure. These systems are selected from different types of application areas. Through implementing a variety of systems, universalness of normally-off computing is confirmed. Also we introduce our “Normally-Off Computing Project”, which supports these practical developments.

Takashi Nakada, Shinobu Fujita, Masanori Hayashikoshi, Shintaro Izumi, Yoshikazu Fujimori, Hiroshi Nakamura

Chapter 7. Related Research & Development

Abstract

Energy consumption is one of the most important problems in the world. To take a general view of activities which focus on energy saving, related research and development in Germany, US and Japan are surveyed and introduced. In each area, different types of activities are observed depending on their policies such as government initiative or private initiative.

Jun-ichiro Yoshikawa

Chapter 8. Conclusion

Abstract

In previous chapters, we introduce idea, methodology of “Normally-Off Computing” with a wide variety of examples. In this chapter, we explain expectation and future aspect of normally-off computing.

Takashi Nakada, Hiroshi Nakamura

Titel: Normally-Off Computing
herausgegeben von: Takashi Nakada
Hiroshi Nakamura
Verlag: Springer Japan
Electronic ISBN: 978-4-431-56505-5
Print ISBN: 978-4-431-56503-1
DOI: https://doi.org/10.1007/978-4-431-56505-5