Getting Started with OpenVMS: A Guide for New Users
A practical introduction to OpenVMS terminology and approach to common concepts.
TABLE OF CONTENTS Getting Started with OpenVMS: A Guide for New Users
Chapter 2: Hardware Platforms Supporting OpenVMS
As described previously, the OpenVMS operating system was originally designed for the VAX computer. Later, the system was ported to the Alpha series of processors, and, as this book is being written, it is being ported to the Intel Itanium line of processors. Let's have a brief comparison of these three architectures, highlighting the most important characteristics of each.
The VAX
As mentioned earlier, the VAX architecture was designed hand-in-hand with the VAX/VMS operating system. This is believed to have been the first time this approach had ever been used for an interactive computer system. Several hardware features were designed specifically to assist with the VMS operating system functions, such as selecting which task to run next ("context switching") and manipulating linked lists of data structures.
The VAX is a 32-bit CISC architecture. The term "32-bit" means that the natural size of a datum used by the CPU is 32 bits (4 bytes) in size. CISC stands for "complex instruction set computing." In short, this means that the VAX has numerous instructions of different in-memory sizes, and they vary in their execution times.
True to its scalability goals, the VAX processor lies at the heart of computers varying enormously in size, speed, and capabilities. The fastest VAX machine is several hundred times quicker than the slowest, while storage capacity and physical size vary by corresponding amounts. The biggest, fastest VAX systems achieve performance comparable to mid-range IBM 3090 mainframe systems.
The VAX is truly a well-engineered architecture, one that is...
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