The Art of Software Thermal Management for Embedded Systems

By Mark Benson

This book introduces Software Thermal Management (STM) as a means of reducing power consumption in a computing system in order to manage heat, improve component reliability and increase system safety. Readers will benefit from this pragmatic guide to the field of STM for embedded systems and its catalog of software power management techniques. Since thermal management is a key bottleneck in embedded systems design, this book focuses on root cause of heat in embedded systems: power. Since software has an enormous impact on power consumption in an embedded system, this book urges software engineers to manage heat effectively by understanding, categorizing and developing new ways to reduce static and dynamic power consumption. Whereas most books on thermal management describe mechanisms to remove heat, this book focuses on ways for software engineers to avoid generating heat in the first place.

• Language: English
• Publisher: Springer
• Release date: Jan 3, 2014
• ISBN: 9781493902989

Book preview

Part 1

Foundation

Mark BensonThe Art of Software Thermal Management for Embedded Systems201410.1007/978-1-4939-0298-9© Springer Science+Business Media New York 2014

Thermal performance is the new bottleneck in embedded systems design. As processing requirements have increased, and physical device sizes continue to decrease, it has become more and more difficult to get heat out of embedded systems.

Excessive heat generated by consumer cell phones and tablets and other electronic devices can reduce component reliability, reduce performance, or even cause discomfort or personal injury when in close contact with skin. This is especially true when the device is in an enclosure without fans or other avenues of convection.

Heat problems such as these affect nearly every electronic device, and particularly those with high computational requirements such as video streaming devices, automobile infotainment systems, high-performance factory equipment, portable hand-held industrial instrumentation, implantable medical devices, and multimedia military combat radios.

The fundamentals of heat transfer are based in the laws of thermodynamics, and are studied by physicists, mechanical engineers, material scientists, and chemists. Researchers and corporations are putting forth great effort to invent solutions to get unwanted heat out of a system quickly and efficiently.

Much focus has been placed on the topic of heat transfer and mechanical or chemical means to extract heat from a system effectively. These are good and fine advancements. However, software engineers play a special role in thermal management since software dictates the types and amounts and durations of computation, all of which will require power and produce heat. Software helps us minimize the root cause of heat in embedded systems (power) and is the focus of this book. In this part, the following three chapters introduce The Art of Software Thermal Management for Embedded Systems and the goals of this book.

Chapter 1 Introduction: In this chapter, we introduce the premise of the book and goals, including a discussion of the microcontroller market, existing thermal management solutions, and whether Software Thermal Management is a science, an art form, or both.

Chapter 2 Landscape: This chapter describes the landscape of problems to solve and the relationship between Software Thermal Management and other adjacent disciplines.

Chapter 3 Roots: In this chapter, the major concepts of the field of Software Thermal Management are explained, including a discussion of its maturity and future outlook.

By the end of this part of the book, you should have a good grasp of the field of Software Thermal Management, its origins, major problems, and general approaches for solving problems that arise.

Mark BensonThe Art of Software Thermal Management for Embedded Systems201410.1007/978-1-4939-0298-9_1

© Springer Science+Business Media New York 2014

1. Introduction to Software Thermal Management

Mark Benson¹  

(1)

Exosite, 5079 Arrowood Ln N, Plymouth, MN 55442, USA

Mark Benson

Email: [e-mail]

Abstract

Software Thermal Management is the study and application of managing the thermal performance of a system using software. This chapter introduces the concept of software thermal management, the growing need for it given the forward-looking growth of the microcontroller market, and a discussion of whether Software Thermal Management is a science, an art form, or both.

The empires of the future are empires of the mind.

Winston Churchill.

1.1 Introduction

Thermal management in embedded systems has become a difficult problem, as shown in Fig. 1.1. This is due to a few reasons:

1.

Processor frequencies are increasing. Faster frequencies mean faster switching. Faster switching consumes exponentially more power and thereby necessarily dissipates more heat. This is a problem and the problem is getting worse.

2.

Processor and device sizes are decreasing. A smaller size means a smaller thermal mass. A smaller thermal mass makes it more difficult to transfer heat quickly. Heat is a natural byproduct of work done by electronic devices and excess heat can be detrimental to the functionality and reliability of the device.

Most studies on thermal management deal with mechanisms to remove heat. However, this book takes a different approach, and focuses on ways to reduce heat by consuming less power in the first place.

This is a software book for software or electrical engineers, and is broken into two parts:

Fundamentals of software thermal management

A catalog of software thermal management techniques and frameworks.

At the end of the book, a set of checklists are provided to help incorporate the ideas contained in this book into a product or software development life cycle process.

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Fig. 1.1

In electronic devices, power is dissipated in the form of heat. Devices and processors are becoming faster, more powerful, and smaller. This is becoming a growing concern as the extra heat can cause component failure or reduced effectiveness

1.2 Purpose

The purpose of this book is to explain the concept of Software Thermal Management to software engineers. Since thermal management and thermal performance is so important for many systems, it is especially critical that software engineers understand the challenges and contribute to the solution as opposed to merely leaving it up to the mechanical engineering or electrical engineering teams.

The book has been written for the following reasons:

1.

Another book on software thermal management like this does not exist. Although books do exist on the topic of power management, the goals of those books is to reduce power primarily to save battery power or to save energy (cost, environmental impact) as opposed to being concerned primarily with thermal performance.

2.

There is a need for a book like this that explains the basic mechanics of thermodynamics and dynamic scaling concepts in microprocessor design to software engineers. Software engineers do not usually have to study thermodynamics in school. Computer science majors usually only touch on hardware design concepts, but not physics or thermodynamics. Computer engineering majors will blend electrical engineering and software engineering, but not mechanical engineering studies, necessarily.

There are numerous Ph.D. dissertations and academic papers that deal with esoteric aspects of creating dynamic power management systems [3, 4, 6, 9, 10, 12–14]. However, in almost all cases, the goal is to simply reduce power when unneeded and increase power when demand is present. The works are intended to be read by like-minded folks that already understand the fundamentals of electronics. There is a noticeable lack of material helping software engineers participate not only in the act of power management in embedded systems, but also thermal software management in embedded systems.

To help meet this need, this book discusses software thermal management in embedded systems, and the material is targeted towards software engineers. A key tenant of the book is that the primary way to manage heat in embedded systems is to manage power. It includes pragmatic approaches that have been used by the author in real product development situations to manage complex thermal performance issues with the aid of software.

1.3 Audience

This book was written for software engineers. Hardware expertise is not a prerequisite. Knowledge of thermodynamics is also not a prerequisite. Some prior familiarity with embedded product design, however, is helpful.

By learning about thermal management, it is the hope that software engineers can play a more active role in the overall thermal and power performance of the system. They can work with mechanical engineers to facilitate the flow of heat, with electrical engineers to pick processors and design power-gating circuits, and ultimately produce better, safer, and more reliable products as a result.

1.4 Scope

This book focuses on the root cause of heat in an embedded system: power. And since software has an enormous impact on power consumption in an embedded system, we need to understand, categorize, and develop new ways to reduce dynamic and static power. In this way, software engineers can contribute more significantly to the study and practice of heat transfer problems and solutions as opposed to merely leaving it up to the physicists, mechanical engineers, chemists, and material scientists.

Software Thermal Management (STM) is the art of reducing power consumption in a computing system as a way to manage heat, improve component reliability, and increase system safety. The scope of this book is to provide an introductory narrative and pragmatic guide to the field of STM for embedded systems, to catalog Software Thermal Management techniques, and to call for future areas of research and development within the field.

STM is an immature field that stands on the shoulders of giants—without physics, material science, chemistry, and semiconductor design and fabrication technologies, none of it would be possible. Although there are plenty of books and research on the topic of heat transfer, plenty of books on semiconductor design, and plenty of books on software engineering, this book is unique in that it brings all three together into a view that software engineers can digest.

The study of heat transfer, which aims to understand and control the flow of heat through a system, has become intensely important as embedded systems, most notably consumer devices that require a high level of multimedia performance and also require very good battery performance, become mainstream.

The processors that drive these types of systems will burn up if they are turned on fully and for long periods of time. Therefore, it’s important to be able to turn them on when needed, turn them off when not needed, and employ a variety of additional techniques to manage dynamic and static power (and heat) in a way the produces high quality, reliable, and safe systems.

This book provides an overview of thermodynamics for software engineers and provides an overview of electrical engineering concepts that are necessary for software engineers to know in order to manage the thermal performance of a system. This book does not intend to provide novel information about thermodynamics or silicon fabrication techniques. Rather, it is a book about software and how software must play a central role in order for an embedded system to achieve adequate thermal performance.

In Part II of this book, the catalog of techniques is not meant to be exhaustive. Rather it is intended to provide a list of techniques that give software the biggest areas of opportunity to affect the thermal performance of a system. There are advanced aspects of power savings in the design of semiconductors such as Active Well Biasing (AWB) that are not covered in this book.

1.5 Goals

Software thermal management is a field of study that until recently, was not given a name [5]. Because STM is so new, the goals of this book are primarily based on the desire to introduce the concept, narrate the need and solution space, and provide a taxonomy of techniques to show how software thermal management should start to think about the design problems involved in this new and budding field.

Specifically, the goals of this book are threefold:

1.

To lay the foundation of the field for Software Thermal Management. Although adjacent fields (software power management, dynamic power management) address some of the same topics, the field of Software Thermal Management is unique in its goals and solution optimizations.

2.

To describe a catalog of techniques, frameworks, and optimizations for the field of Software Thermal Management. Microprocessor vendors each have their own brand-names that they ascribe to thermal management strategies and approaches. These various brand names cause confusion since they often describe the same thing, but have subtle (but substantive) differences that we must unravel. By providing a catalog of techniques, the hope is that the standardized names and terminology can make knowledge about this field more cohesive, organized, and clear.

3.

To offer a set of checklists that aid in the process of institutionalizing Software Thermal Management concepts into a product development process. Any set of concepts or design ideas, if they are good, should be systematized across the organization. Thermal management should not be an after-thought. Rather, it should be considered from the outset, designed with thermal performance requirements in mind, tested under target environmental