© Copyright IBM Corp. 1998 21
Chapter 2. Hardware Overview
This chapter introduces the standards and architectures that are shared
between the RS/6000 43P Series systems. The discussion encompasses the
following topics:
• PowerPC microprocessor RS/6000 Platform Architecture (RPA)
• Hardware design
• Processor subsystem
• SMP hardware characteristics
The general architectures discussed in these sections help build an overall
appreciation for RS/6000 hardware.

2.1 The RS/6000 Platform Architecture

The RS/6000 Platform Architecture (RPA) introduces a comprehensive
computer system hardware-to-software interface definition, combined with
minimum system requirements, that enables the development and porting of
software to a range of compatible computer systems from portables through
servers. These systems are based on the PowerPC microprocessor, as
defined in the
PowerPC Architecture: A Specification for a New Family of RISC
Processors. Both the RS/6000 43P 7043 Model 150 and Model 260 are RPA
compliant.

2.1.1 The RS/6000 Platform Architecture Introduction

The RPA is essentially a combination of its predecessor, the PowerPC
Microprocessor Common Hardware Reference Platform (shortened by the
industry to be known as the PowerPC Platform) and some IBM architecture
extensions. This platform architecture officially came into being in August of
1997.
Prior to IBM’s RPA, an alliance existed between Apple, IBM, and Motorola
that developed a common hardware platform with the purpose of defining a
system that would become the pervasive open industry standard, from single
user to server configurations. As a result of this alliance, the PowerPC
Platform emerged. The PowerPC Platform, previously known as CHRP, is a
superset of the earlier PowerPC Platform Specification (PRep) system
architecture. The Apple, IBM, and Motorola alliance is no longer functional.
A key benefit of the RPA specification is the ability of hardware platform
developers to have degrees of freedom of implementation below the level of