VLSI Digital Signal Processing Systems: Design and Implementation

17.1    INTRODUCTION

Historically, performance characteristics of digital systems have been synchronous with circuit speed or processing power. For example, in the world of microprocessors, performance is often measured in terms of MFLOPS (millions of floating point operations per second) or MIPS (millions of instructions per second). The cost of the digital system is dependent on the implementation strategy being considered. For VLSI system design, there is a fair one-to-one correspondence between silicon area and cost. Consequently, increasing the implementation area tends to result in higher packaging costs as well as reduced fabrication yields with both effects leading to increased product cost. In addition, improvements in system performance generally come at the expense of silicon area. Therefore, historically, the task of VLSI designers has been to explore the AT (area-time) trade-offs and strike a reasonable balance between these often conflicting objectives.

Recently, it has been found that area and time are not sufficient metrics for evaluating the system performance. Power consumption is another very important metric. Until recently, power consumption was only a secondary concern in comparison to area and speed. However, this thinking has begun to change in recent years and power is being given comparable weight to area and speed considerations. Many factors contribute to this new trend. Perhaps the most visible factor has been the phenomenal growth of portable electronics. ...