Microsoft announced in September 2003 that it would support AMD's 64-bit Opteron and Athlon 64 microprocessors with unique Windows server and client OS versions. The company then spent much of 2004 building those 64-bit products and improving them to include the features from the most recent service pack for each version. Now that Intel has announced support for the x64 architecture—as the AMD64 design is now known—Microsoft's new 64-bit OSs will be more popular than first anticipated. And because the x64 platform is compatible with today's 32-bit OSs and software, customers who purchase x64-based servers, workstations, or PCs today will be able to upgrade to 64-bit Windows versions in the future and still run all their existing applications. With the final product release set for the first half of 2005, just 1 year before the company ships 32-bit and 64-bit versions of Longhorn, we're finally entering an era of widespread 64-bit computing. Here's what you need to know about Windows 2003 x64 and XP Pro x64.

Windows 2003 x64
To support the AMD Opteron and Intel Xeon Extended Memory 64 Technology (EM64T) processors, Microsoft will release two Windows 2003 versions in the first half of 2005. These products, dubbed Windows 2003 Enterprise x64 Edition and Windows 2003 Standard x64 Edition, will provide all the functionality and features of Windows 2003 Enterprise Edition and Windows 2003 Standard Edition, respectively, along with the improvements from Windows 2003 Service Pack 1 (SP1). Windows 2003 Standard x64 Edition supports as many as four processors and as much as 32GB of RAM; Windows 2003 Enterprise x64 Edition supports as many as eight processors and as much as 64GB of RAM.

The x64 versions of Windows 2003 support a lot more memory than their 32-bit siblings and let you scale Microsoft Exchange Server and Active Directory (AD) data stores and Microsoft SQL Server databases to new heights and support more simultaneous Windows 2000 Server Terminal Services users. The x64 versions of Windows 2003 also sport tangible performance benefits over 32-bit systems. "We tested a whole series of workloads \[on x64\]," Microsoft Senior Vice President Bob Muglia said. "Some workloads just don't benefit that much from 64 bits, but having a 64-bit OS on there gives you certain advantages. \[With\] other workloads—even if the app is 32-bit—you get a huge benefit by running on a 64-bit OS. The most extreme example of that is Terminal Services, because it's limited by the amount of physical memory in the box, in terms of capacity. So even though it's a 32-bit application, you can now run a lot more users simultaneously on the same computer. And these 4-way \[servers\] are blazingly fast."

To support its x64 server products, Microsoft will release a 64-bit version of SQL Server 2005 and, eventually, a 64-bit version of its other server products, such as Exchange Server. "We're pretty bullish about the industry turning over to 64 bits pretty rapidly," Muglia told me.

XP Pro x64
At one time expected to be only a subset of XP Pro, XP Pro x64 will include nearly all the features from its 32-bit counterpart. The only missing features are those that are impossible or undesirable to implement on the x64 platform—such as the legacy 16-bit subsystem that lets 32-bit Windows versions execute DOS and Windows 3.x applications—and older protocols such as NetBEUI and AppleTalk that have outlived their usefulness. "The only surprise here is that certain 32-bit applications still use a 16-bit installer," Brian Marr, product manager of the Windows Client Group, told me. "So those won't install on XP x64. We're treating those problems as bugs and are working with the application makers to get 32-bit installers completed for those applications."

XP x64 is well-suited to the kinds of memory-intensive tasks (e.g., analysis, engineering and scientific modeling) typically associated with 64-bit computing. And because the system is backward-compatible with most 32-bit software, such as Microsoft Office 2003, Adobe PhotoShop, and even most games, you can replace PCs in your organization with systems based on XP x64 without requiring any end-user training. The x64-based systems integrate with Windows networks seamlessly, working identically to their 32-bit cousins. The primary advantage to a 64-bit desktop, however, is performance. According to Microsoft, systems based on the x64 platform achieve a small performance bump simply by running the native 64-bit Windows OS and an even bigger bump when you run these systems in combination with 64-bit software. And 64-bit systems can access lots of RAM: The AMD x64 line can access as much as 1TB of RAM; the Intel Xeon EM64T can access as much as 64GB of RAM.

Compared to the Itanium version of XP, known as XP 64-Bit Edition, Version 2003 SP1, XP x64 has a more complete feature set, works on standard PC hardware (albeit hardware that includes an x64 processor and 64-bit device drivers), and performs better. "We see XP x64 being much more widely adopted than the Itanium version," Marr told me. "\[The processors\] are already successful with high-end consumer-oriented PCs and workstations. Plus, that product will have all the features from XP \[32-bit\]. The Itanium version will still be used on highest-end workstations for analysis and engineering. But we aren't going to be adding as wide a set of additional features as we have for x64."

Protecting Your Investment
To give customers added incentive to purchase x64-based servers and PCs today, Microsoft will provide a technology exchange program in the first half of 2005 that will let customers deactivate their 32-bit Windows licenses in exchange for an equivalent 64-bit OS for free. However, the exchange program comes with one caveat: The x64 versions of Windows don't support upgrades, so you'll need to reinstall the system from scratch. After you install the 64-bit system, you'll be able to reinstall virtually all your 32-bit applications and take advantage of 64-bit performance and scalability benefits. One sticking point might be finding 64-bit drivers for all your hardware, but Microsoft is confident that hardware makers will address 64-bit drivers and notes that the XP x64 beta already ships with more device drivers than did the initial 32-bit version of XP.

Although the sputtering fate of the Itanium has been puzzling to some and justifiable to others, clearly the x64 platform is the hardware wave of the future. Beginning in 2005, you'll have little reason not to purchase x64-based hardware, even if you simply run existing 32-bit Windows versions on that hardware for a while. And as we move forward, it's equally clear that new purchases should include both 64-bit hardware and 64-bit Windows versions. Once these versions of Windows ship broadly, there'll be no turning back to the dark ages of 32-bit computing. It's time to jump on the x64 train.