Low Power Techniques for Greener Hardware

Introduction

The use of Information and Communication Technology (ICT) has grown manifold in the past decade. ICT technology and devices have, due to extensive networking, made the world smaller. The large proliferation of these devices has led to considerable power consumption. One approach towards greener ICT is to optimize the power consumed by numerous ICT devices around us.

Examination of the overall structure of IT usage in daily life leads to its categorization into two areas – Personal resources and Common resources. Personal resources include mobile phones, desktops, laptops, palmtops, PDAs etc. to name but a few. Common resources comprise of bigger infrastructural elements like routers, network switches, enterprise servers, server farms for data centres and so on. Most of the above mentioned devices are digital devices or contain large sections of digital hardware and they are shown in Figure 1. The feature additions to the electronic gadgets and the processing requirements of large systems have made it almost mandatory to design and develop hardware which consumes less power, making power a primary design constraint for digital designs at all levels.

Figure 1.

Commonly used ICT equipments and information flow

We shall discuss the basic techniques of power reduction in both these categories of IT devices.

Personal Ict Devices

Personal ICT devices include desktops, laptops, mobile phones, PDAs etc. The operation of personal ICT devices can be simplified into three main functions: Communication, Computation and User interface. As the size of these devices keeps shrinking, the demand for reducing the power consumption keeps increasing.

These devices are widely used in today’s IT age. As the technology advances, these devices have evolved into stand-alone electronic equipments encompassing several applications. Consider a normal mobile phone that has now become an integral part of ICT system and human life. The same phone before a decade was used as a communication equipment, providing some basic features like phone number memory, call list and some basic settings. Today, mobile phones possess several features and are used for purposes ranging from communication to entertainment to health care. All these features require a fairly large amount of hardware. The shrinking chip geometries and the Very Large Scale Integration (VLSI) industry following the Moore’s law have been the basis for all the exponential growth that these ICT devices have registered.

However, with the increasing need for hardware, these devices also need processors which are low power, especially because these are battery powered. The battery size is also a concern for making compact mobile phones. To support a large number of features, a high-performance processor is required.

Similarly, in case of other personal ICT devices like desktops and laptops, there have been similar trends and these devices have a need of hardware acceleration for graphics and other multimedia-intensive applications. With the need to have near real-time processing capabilities, the processors as well as the operating systems are tuned to achieve optimal performance. Once again, the power utilization of the processors has increased several folds. There are several methods being considered for greening of this hardware by making it low power. The maximum utilization of power is by the microprocessor or the Central Processing Unit (CPU). Power is also utilized in the cooling of this microprocessor chip (integrated circuit), which is usually done by using a fan on a casing (heat sink) mounted over the chip.

As technology advanced, there was a need to control the power dissipation in the processor chips. This is because; more features in hardware lead to more logic and thus, need for more solid state devices that form these logic circuits. Now we shall focus on how power dissipation occurs and then subsequently look at the solutions. Of course, low power system design is a subject by itself, but we shall look at it from its overall contribution in greening the ICT process.