History

Throughout the 1960s, Digital developed and sold a very successful line of computers known as the PDP series. In the early 1970s, Digital began to recognize that the larger programs and data sets being developed were beginning to outgrow the limitations of the 16-bit PDP architecture. Increasingly, programmers had to split large programs into smaller units that would run on their computers. One PDP model, the PDP-11/70, was designed as an attempt to increase the useful data capacity of the PDP hardware, but it was still restricted by having to use portions of the same 16-bit software architecture.

Digital began to envision a line of computers that would be compatible with the PDP series and, yet, lift the restrictions on program and data size resulting from the PDP design. In March 1975, a team was assembled whose purpose was to propose a "32-bit PDP" product. The result was a new line of computers, the VAX, and a new operating system designed specifically for it, VAX/VMS.

The first VAX systems were ready in late 1977, a remarkably short time for the development of a hardware architecture and a new operating system. After the introduction of the VAX, the PDP line was developed for many more years. The PDP-11 continued to serve markets where a 32-bit system was not needed, or where its excellent real-time data-collection capabilities were required. Of course, the VAX became Digital's flagship product.

The VAX and VAX/VMS were enormously successful, both in business and in academia. So many universities had VAX computers in their labs that computer science graduates of that time were sometimes referred to as "the VAX generation." The VAX was smaller than a mainframe, but larger than a microcomputer. It was about the size of what was then known as a "minicomputer," but had better performance. The VAX came to be classified as a "supermini."

Over its first 15 years, the VAX architecture underwent numerous upgrades in hardware technology. Its CPU performance, memory capacity, disk capacity, and I/O performance all increased by several orders of magnitude. The later examples of the VAX architecture featured literally hundreds of times more performance than the original. All this was achieved with very little change to the original VAX architecture design.

In the 1980s came the MicroVAX; a VAX small enough to sit beside a desk, running a subset of VAX/VMS called MicroVMS. Within a few years, the MicroVAX had advanced to the point that MicroVMS was no longer required; all subsequent machines would run the full VAX/VMS system. The MicroVAX II, which came in five major variants, proved so successful and so flooded the marketplace that during the late 1980s, the average VAX system manager had less than three years of experience.

The VAX and MicroVAX lines were developed in parallel, and the MicroVAX spawned a line of graphics workstations called VAXstations. These machines were the first VAX/VMS machines to have a graphics display and mouse (although previous VAX machines did have some limited graphics capabilities via graphics terminals such as the VT240).

In 1991, Digital announced that the VAX/VMS operating system would be renamed "OpenVMS."

The late 1980s and early 1990s had seen popularity gains in "open" systems. One rather simplistic definition of "open" is a system for which the source code is readily available to anyone. Sometimes, users may develop enhancements that eventually become part of the official version.

Critics wondered aloud, "How can you call a proprietary system like VMS 'open'?" But OpenVMS proponents point out that OpenVMS passes many tests for an open system and, in fact, earned several open-systems certifications before some versions of UNIX, the system around which much open systems development is based. The change of name was liked by some OpenVMS users and disliked by others.

At about the same time as the name change, Digital's new hardware platform supporting OpenVMS became available, the Alpha AXP architecture.

Enter the Alpha AXP

The VAX architecture was developed to go beyond the 16-bit capabilities of the PDP-11. The 32-bit VAX environment provided a luxury to programmers who no longer needed clever tricks to fit applications and data into a 16-bit machine. However, applications continued to grow, and today some high-end applications require even more addressing space than 32 bits can provide.

Today, a 32-bit architecture is more than adequate for most computing tasks; virtually all new personal computers are still 32-bit machines. But some applications, including weather forecasting, fluid dynamics modeling, and very large databases need still more addressing capability.

Digital recognized the impending need for such a machine and developed the Alpha AXP architecture. The Alpha is a full 64-bit architecture with an addressing space as impressive in 1992 as 32 bits was in 1977. To illustrate, a 32-bit machine has approximately four thousand million bytes of addressing space. A 64-bit machine has four thousand million bytes for every byte that a 32-bit machine has.

The Alpha was designed to run multiple operating systems, which included OpenVMS, Digital UNIX, and Microsoft Windows NT. After about a decade of development, the first Alpha AXP computer and OpenVMS AXP V1.0 were shipped in 1992. By the late 1990s, revenues from Alpha systems far exceeded those of the VAX, which itself had been very successful. The VAX and Alpha versions of OpenVMS were developed roughly in parallel until the late 1990s, when the discontinuation of the VAX architecture was announced.

In 2001, Compaq Computer Corporation (which had acquired Digital a few years before) began porting OpenVMS to a third hardware architecture, the Intel Itanium. The Alpha processor line will undergo upgrades through 2004, and the last major variant, the EV79, will be the basis for what is now being called "the next generation server family," to be released in late 2004 or early 2005. Afterward, the Itanium architecture, described next, will be the primary 64-bit platform for OpenVMS.

Enter the Itanium

In 2001, Compaq Computer Corporation announced plans to port OpenVMS to the Intel Itanium processor, also known as the IA-64. At the time of this writing, the Itanium version is not available for testing, but Intel has made detailed technical documents available for review. The description of Itanium contained here is based on those documents.

The Itanium is a 64-bit architecture, featuring the same amount of addressing space as the Alpha. Those features of the Alpha that allow it to emulate complex VAX characteristics and to support multiple operating systems, collectively known as "PALcode," will have Itanium counterparts. Specifically, certain Alpha-style PALcode functionality will be included in the Itanium version of OpenVMS itself, while other portions may be contained in a computer's firmware. In the Alpha design, PAL stands for "privileged architecture library," and under Itanium, "processor abstraction layer," but the functionality is quite similar. Some combination of hardware, firmware, and software PALcode support will provide an environment for the successful porting of OpenVMS to Itanium.

Based on comparisons of the VAX, Alpha, and Itanium architectures, the porting of OpenVMS from Alpha to Itanium should prove to be less difficult than the porting from VAX to Alpha was a decade ago. The first OpenVMS Itanium machines are scheduled to be available for third-party testing in 2003 with the production release scheduled for early 2004.

Continued Support for VAX and Alpha Systems

Itanium will eventually become the primary platform for OpenVMS, but for the next several years, OpenVMS will be available on three separate hardware architectures: VAX, Alpha, and Itanium. Existing VAX and Alpha systems will eventually be replaced by Itanium systems, but there will be a large amount of overlap during the next several years.

Over 500,000 VAX systems were sold during more than two decades of development, and many are still in service. As of 2002, some VAX systems are still available through certain channels, and new generations of the Alpha architecture are under development at the time of this writing.

In May 2002, Compaq merged with Hewlett-Packard. Compaq had previously made commitments to support existing VAX machines until at least 2010, and existing Alpha systems for significantly longer. Hewlett-Packard has since affirmed its intention to honor these commitments.