Digital System Clocking: High-Performance and Low-Power Aspects

CHAPTER 9

MICROPROCESSOR EXAMPLES

The purpose of this chapter is to recapitulate the material presented in this book through various examples. It also presents the state of the art in microprocessor design from the standpoint of clocking and clocked storage elements. In this chapter we analyze the clocking techniques and clocked storage elements used in four leading microprocessor design houses: the Intel Corporation, Sun Microsystems Inc., the Digital Equipment Corporation (unfortunately, this latter company is not in existence any longer as of the writing of this book) and the IBM Corporation. We have chosen to emphasize different aspects each time we describe the techniques and designs used, and to go into depth on different solutions for clocking of high-performance and low-power systems.

In the section describing clocking techniques used in Intel® microprocessors we describe an active clock deskewing technique that was used in Pentium® processors. This discussion supplements the subject of clock distribution that was only briefly touched on in Chapter 1. We do not place much emphasis on the clocked storage elements used in Intel microprocessors in this section for two reasons: first, Intel never explicitly published the CSE topologies used in their microprocessors, and second, we have presented those CSE topologies known to us in the previous chapters.

The section describing techniques used by Sun Microsystems Inc. presents an overview of the development of the semidynamic ...