Low Power Microprocessor Design

Simon Anthony Segars

Abstract

Over the past few years low power has become an important design criteria for electronic equipment. This has come about mainly due to the rapid market growth of portable and hand held devices such as laptop computers and mobile phones. Most of these products include an embedded microprocessor and this thesis is concerned with determining how a microprocessor may be designed for low power.

There are a number of factors which must be considered before undertaking a design which targets low power. Firstly, it must be determined what the major sources of power consumption are in current designs so that they can be optimised in the future. In this work the power consumption of the ARM6 microprocessor is analysed. It is shown that the blocks with the highest power consumption are the ALU, Register Bank and Instruction Decoder. These blocks are then analysed in greater detail, and suggestions are made for how lower power implementations could be achieved.

Secondly, the issue of power prediction must be considered. It is important that power can be predicted early in the design cycle. However, most prediction techniques involve simulating a completed design and although this is useful for determining where power is consumed in existing designs, it is no help early in the design cycle. Various power analysis methods are presented and used to determine the ARM6 power consumption. Their strengths and weaknesses are then compared.