IBM RS/6000 - Manual (Page 28)

Independent software vendors (ISV) would like to develop for a large, installed base
of hardware systems and on as few operating system platforms as possible. For
this to happen, an industry standard computer architecture is required. The time
has come to define a new architecture in this area which has the following key
features:
The ability to allow hardware vendors to differentiate
The ability to use industry standard components and interfaces
The ability to support optimization of application performance
Compatible Operating Systems
This type of open system architecture allows hardware system vendors to
develop differentiated, yet compatible, systems. Each system is able to run any
of the compatible operating systems as well as the applications written for these
operating systems and system architecture.
1.2 Introducing the PowerPC Reference Platform Specification
The PowerPC Reference Platform Specification provides a description of the
devices, interfaces and data formats required to design and build a PowerPC-based
industry standard computer system. It is written to create a hardware, which when
coupled with the hardware abstraction software provided by the operating system or
hardware-system vendors, allows the computer industry to build PowerPC systems
which all run the same shrink-wrapped operating systems and the same
shrink-wrapped applications for those operating environments.
It gives system developers the freedom to choose the level of market differentiation
and enhanced features required in a given computer environment without carrying
obsolete interfaces or losing compatibility.
This specification defines the minimum functional requirements for a compliant
PReP implementation. It also provides a list of recommended hardware
subsystems, devices and interfaces.
Operating system vendors may use this specification as a reference to determine
the level of functionality required in a hardware abstraction layer. The specification
shows the hardware subsystems that are likely to change and therefore may need
hardware abstractions.
The PowerPC Reference Platform Specification is written primarily for system
developers. It contains operating-system-specific descriptions and references to
their hardware abstraction approach.
This specification also describes a reference implementation which is a fully
functional PReP system design supporting all operating systems and applications
that are being ported to this reference platform. This reference implementation
provides an example to which system developers can compare and gives them a
better understanding of their own design goals.
This specification supports all 32-bit PowerPC processors and is intended to cover
the following systems:
4 Introduction to PCI-Based RS/6000 Servers