Investment Protection
The triple protection that Itanium architecture offers is for legacy software, legacy hardware, and legacy data. This was the second major goal we had when we began the project. We wanted to protect the customer's investment in IT infrastructure as much as possible.
Legacy Software
It turns out that when you analyze an organization's IT investment, the bulk of it is not in the hardware. Most of the investment beyond the people is in the software and the legacy data that is stored. So one of the goals when developing Itanium was being able to run—even though it would be at a lower speed than a native binary—the existing applications coming from both the IA-32 world as well as the PA-RISC world.
HP built this investment protection for PA-RISC into HP-UX, our version of the UNIX®[2] operating system. For the IA-32 world, the backward compatibility is also implemented, allowing even more flexibility. This allows Itanium-based systems to run Linux applications and Microsoft Windows applications without change.
[2] UNIX is a registered trademark of The Open Group.
The idea is that the user won't have to immediately go out and update new software applications. Most customers will want to update some applications in order to take full advantage of the phenomenal speed gains the Itanium processor family makes available, but in some cases, it's just not a critical issue. For example, the application in question could be a utility routine that runs in the background, say to monitor events and generate reports. An example would be HP's Openview suite of system management tools. In other words, it would be a program that would stand to benefit extremely little from an performance upgrade, and yet would be annoying or laborious to re-compile or re-write.
A second problem that IT organizations often run into is in their own proprietary software. This is where the source code has been lost and the person who wrote it is no longer available to consult. The cause of this loss is irrelevant. What matters is that there is no one around to redesign the program on short notice. With the investment protection, built into Itanium-based systems so that a redesign isn't necessary, this issue is neatly avoided.
Legacy Hardware
Hewlett-Packard's long-standing policy on legacy hardware was extended to the Itanium architecture before the project even began in earnest. The goal here was to build systems that we could upgrade from PA-RISC microprocessors by simply replacing the systems board with future Itanium processors installed. So most of the Hewlett Packard PA-RISC systems that we've built and launched in the past year have the ability to be upgraded to versions of the Itanium processor family.
Legacy Data
Enterprises have huge databases built over time on their IT systems. This data, if built under a PA-RISC and HP-UX environment, is stored in a “big endian” format. If you move to a system, which is “little endian”, the user can't simply plug the older disk with its data into the new system. (See Appendix A for a definition of “endian.”) Instead, the data will need to be converted before being used. In order to protect the data of our enterprise customers on HP-UX systems, as well as data that is stored in “little endian” on Windows or Linux based systems, we made sure that Itanium was endian neutral and could handle data in either format.