Chapter 1. PA-RISC 2.0 Architecture

Before we dive into HP-UX itself, we should have a look at the underlying system architecture. The very nature of an operating system requires that it be aware of the architecture it's running on. The operating system's kernel insulates the user applications from the hardware, making the architecture mostly transparent to the applications. But the kernel itself has to work directly with the hardware and so has to be designed to run on a particular type of hardware.

HP-UX has been implemented on a variety of platforms, among them the Motorola 68000 family, HP's PA-RISC family, and the new Itanium family. In this book we concentrate on the PA-RISC architecture. The 68000 versions of HP-UX are long obsolete, and the Itanium versions are new enough that there are few implementations in use. The vast majority of HP-UX systems are running on PA-RISC hardware.