Introduction to Multiprocessors - Fundamentals of Computer Organization and Architecture - page 235

& CHAPTER 11

Introduction to Multiprocessors

Having covered the essential issues in the design and analysis of uniprocessors and
pointing out the main limitations of a single-stream machine, we begin in this chap-
ter to pursue the issue of multiple processors. Here a number of processors (two or
more) are connected in a manner that allows them to share the simultaneous
execution of a single task. The main argument for using multiprocessors is to
create powerful computers by simply connecting many existing smaller ones. A
multiprocessor is expected to reach a faster speed than the fastest uniprocessor. In
addition, a multiprocessor consisting of a number of single uniprocessors is expected
to be more cost-effective than building a high-performance single processor. An
additional advantage of a multiprocessor consisting of n processors is that if a
single processor fails, the remaining fault-free n 2 1 processors should be able to

provide continued service, albeit with degraded performance. Our coverage in
this chapter starts with a section on the general concepts and terminology used.
We then point to the different topologies used for interconnecting multiple pro-
cessors. Different classification schemes for computer architectures are then
introduced and analyzed. We then introduce a topology-based taxonomy for inter-
connection networks. Two memory-organization schemes for MIMD (multiple
instruction multiple data) multiprocessors are also introduced. Our coverage in
this chapter ends with a touch on the analysis and performance metrics for multipro-
cessors. It should be noted that interested readers are referred to more elaborate dis-
cussions on multiprocessors in Chapters 2 and 3 of our topic on Advanced Computer
Architecture and Parallel Processing (see reference list).

11.1. INTRODUCTION

A multiple processor system consists of two or more processors that are connected in
a manner that allows them to share the simultaneous (parallel) execution of a given
computational task. Parallel processing has been advocated as a promising approach
for building high-performance computer systems. Two basic requirements are
inevitable for the efficient use of the employed processors. These requirements