64-bit Overview

Both Microsoft and Intel are pushing 64-bit servers like there's no tomorrow. Many of the touted advantages are perfectly real, such as the truly enormous memory support included in the 64-bit architecture. 64-bit servers are perfect for memory-hungry database and data warehousing servers, and the 64-bit architecture offers throughput that makes it perfect for file serving, Internet content caching, and more.

Intel's 64-bit architecture is based around its Itanium processor family. The Itanium is not only a 64-bit processor, but also includes a number of general enhancements over Intel's latest Pentium processors. One major new feature is EPIC, Intel's Explicitly Parallel Instruction Computing architecture. EPIC provides far superior parallel computing, prediction capabilities, and other features that allow Itanium processors to effectively process more instructions at one time. Even though the initial Itanium processors had a clock speed less than half of the then-current Pentium processors, Itaniums were still faster due to their capability to process more instructions in parallel, rather than in sequence.

What About the Competition?

Many folks?including myself?have become accustomed to the competition between AMD and Intel processors. Every time Intel released a new Pentium, AMD wasn't far behind with a new, comparable processor. If you've enjoyed the lower prices created by this competition, you'll be pleased to know that AMD is countering Intel's Itanium with its own 64-bit chip code-named Hammer.

You can get more details on Hammer at www.amd.com. Hammer's architecture isn't intended to be a straight clone of Itanium, although I would expect 64-bit Windows to run on Hammer when it is released.


The Pentium family of processors has always had an ever-growing capability for parallel instruction processing. Unfortunately, many of those capabilities require special efforts on the part of software developers and compilers, so the Pentium processors weren't always working at their best.

Because Itanium represents a whole new line of processors, everyone is starting from scratch. Software developers and compilers will be able to take better advantage of Itanium right from the start.

Itanium 2's system bus runs at a blazing 400MHz, almost triple the speed of the fastest Pentium system busses (and faster than the original Itanium's 266MHz bus). Itanium also includes enterprise-class reliability features, such as enhanced error detection and correction capabilities and an integrated error reporting mechanism?all features that can exist because Itanium isn't based on what came before but is instead a radically new architecture. Obviously, the capability to support up to 256 processors in a single system presents exciting new ideas for some amazingly powerful (and expensive) servers.

As you'll read later in this chapter, Itaniums can fully emulate a Pentium processor, enabling Windows to more easily support 32-bit applications under a 64-bit environment. This backward-compatibility is a good sign for Itanium's longevity in the marketplace because businesses won't have to immediately scrap all their 32-bit software to implement 64-bit computers.