IBM RS/6000 - Manual (Page 27)

To be sustainable and to continue growing, the computer industry must define
computer architectures which allow system and application designs to utilize the
latest silicon, interface, storage, display, and software technologies. The key to
these new computer architectures is the ability of the software to abstract the
hardware from the operating system kernel and applications without sacrificing
compatibility or performance.
Figure 3. PReP Specification Compatibility Model. Abstraction layer separates hardware
and software.
Figure 3 shows the new model specified in the PowerPC Reference Platform
Specification. An abstraction layer separates the hardware from the software. The
advantage of this model is that hardware designers now have room to innovate
without jeopardizing the ability of their platform to run as many operating systems
as possible.
Figure 4. PReP Specification Design Environment
Figure 4 shows, that changing the hardware, for example from hardware level 1 to
hardware level 2, only requires a change in the abstraction layer. No changes are
required in the operating system or in the application itself.
Chapter 1. Introduction 3