The computer industry is about to embark on its next big transition--a shift from 32-bit Windows computers to a new breed of 64-bit PCs and servers. It promises to be as significant as the revolutionary changes brought on 12 years ago by Microsoft's 32-bit Windows NT, which ushered in an era of sophisticated client-server applications. Yet, while the performance benefits of 64-bit Windows are compelling, it could be years of countless upgrades before many companies complete the move.

Microsoft chairman Bill Gates will signal the start of the transition this week at the company's WinHEC conference for hardware engineers in Seattle. Gates is expected to reveal that 64-bit editions of Windows XP and Windows Server 2003 are now available for 64-bit processors from Advanced Micro Devices Inc. and Intel that support the ubiquitous x86 instruction set. PCs and servers equipped with the chips and operating systems will begin shipping from some computer manufacturers immediately.

"It's the biggest thing happening in the computing space," Gates said in an interview last week on Microsoft's Redmond, Wash., campus. And it means Microsoft's business customers will have a decision to make the next time they buy computers. Do they choose 32-bit Windows systems to maintain operating-system consistency with their installed base? Or, for the same price, go with faster 64-bit Windows machines? "Wherever they want more performance, this is a huge opportunity," Gates says.

The current generation of Windows computers--hundreds of millions of PCs and servers worldwide--is bumping against a performance ceiling inherent to 32-bit architectures: System memory is limited to 4 Gbytes. With 64 bits, it's blue sky above: 128 Gbytes of RAM and a potential for 16 terabytes of virtual memory. "It gives us pretty unbelievable headroom," Gates says. That translates into faster performance for many applications, especially those with large data sets, rich graphics, or many users to support.

The ramp-up has been years coming, and it has ramifications for Microsoft's next-generation Longhorn operating system, which will be offered in both 32-bit and 64-bit flavors. Microsoft has been offering a 64-bit version of Windows for Intel's Itanium processors for four years, but flexible computers capable of running both 32-bit and 64-bit apps were needed. The new x64 editions of Windows on newer chip designs from Intel and AMD do just that. "The timing between us and the chip guys is really about perfect," Gates says.

Microsoft's 64-bit operating systems were originally due in the first half of 2004. The software, which the company has been working on for two years, is available in four configurations: Windows XP Professional x64 and Windows Server 2003 x64 in standard, enterprise, and data-center editions. They're priced the same as their 32-bit counterparts.

For most companies, the shift from today's 32-bit Windows systems to tomorrow's 64-bit models will be gradual. "We would definitely not be first adopters," Garrett Grainger, VP and CIO of Dixon Ticonderoga Co., says via E-mail. The manufacturing company will wait for Windows x64's stability to be proven and for 64-bit applications to become widely available. Still, "the power would be welcome," he says.

Since many companies are deeply invested in 32-bit Windows infrastructures, the migration to 64-bit systems will take years. But Microsoft officials believe a changeover is inevitable. "By the end of this year, you'll be hard-pressed to buy a server chip that's not 64-bit, and by end of next year, you'll be hard-pressed to buy a client [chip] that's not 64-bit," says Jim Allchin, group VP of Windows platforms. A new Technology Advancement Program gives customers a few months to think about which way to go. Those who buy 32-bit Windows will have until July 30 to upgrade at no extra cost.

Companies that aren't ready to make the switch won't have to. Because the AMD and Intel chips are dual purpose, it will be possible to run 32-bit Windows operating systems--Windows XP, Windows Server 2003, and Windows 2000, for example--and their familiar 32-bit applications for years. Gates expects 32-bit Windows applications to be around for a stretch. "Not in my lifetime is that likely to change," he says.

Microsoft officials say there's pent-up demand for Windows x64 in two areas: on database and Web servers maxed out by the 32-bit memory cap, and on PCs used for graphics-intensive applications such as computer-aided design, 3-D rendering, and video editing. Gates sees the biggest opportunity in the server market, where Windows Server 2003 x64 will be offered not only as an upgrade to 32-bit Windows servers but as an alternative to 64-bit Unix and Linux servers. More than half the installed base of Windows servers are candidates for 64-bit replacement, Gates estimates.

IDC analyst Al Gillen forecasts that 20% of Windows servers sold over the next 12 months will ship with Windows Server 2003 x64, and the transition for businesses won't be painful. "I'm a believer that x64 technology is a nondisruptive innovation," he says. "As a result, acceptance of it will be very broad over time."

Reuters America Inc., which uses Windows servers widely in its tech infrastructure, has been evaluating 64-bit Windows for about a year. "We think 64-bit is coming and will dominate the industry in due time," says Bill Evjen, a technical director of development with Reuters' platforms group, via E-mail. In addition to assessing 64-bit Windows for internal operations, Reuters is studying its potential for application servers at customer locations that support the company's information services. "We're sure we are going to have customers requesting our offerings in the 64-bit flavor," he says.

Desktop upgrades to Windows x64 probably won't be as widespread as in the server market. "There are a small percentage of people constrained by PC-processor speed," says Michael Cherry, an analyst with Directions On Microsoft. "I'm not going to just drop everything in my Dell machine right now to run out and buy a new machine." Gates agrees, estimating that today fewer than 10% of PCs are candidates for Windows XP x64.

Power users may want the boost. "I have a small group of [CAD] workstations that I want to replace. I need to bump them up," says Steve Wierenga, VP of IT with Ajacs Die Sales Corp., a small distributor of industrial supplies. Wierenga plans to test Windows XP x64 as a potential option.

Longhorn, not Windows XP x64, will be the upgrade path for most Windows PCs. "The big numbers on the desktop will come with Longhorn," Gates says.

The Longhorn client will be based on the same underlying code used for Windows XP x64 but will come with a broad range of new features for users. For example, Longhorn's interface will give users new kinds of information--including a peek at the content inside folders--as they guide a cursor across their PC screens. "When you move to 64-bit [Windows XP], you don't see any change at all. There isn't a pixel that's different," Gates says. "Longhorn is a feature release to make all end-user tasks dramatically simpler than they are today."

Like its customers, Microsoft will find itself in both the 32-bit and 64-bit camps for the foreseeable future. The company is developing 32-bit and 64-bit versions of Longhorn, and when it issues an early snapshot of Longhorn code to hardware engineers this week, it will make both available. It's likely the Longhorn client and the Longhorn server will ship in both forms when they become generally available. The client is due in the second half of next year and the server in the first half of 2007.

So, how long will Microsoft continue to develop 32-bit operating systems now that 64-bit Windows is here? "I don't know. I really don't know," says Allchin, who oversees all Windows development. "I don't think we have finally decided yet." Microsoft's SQL Server 2005 database, due later this year, also will ship in 32-bit and 64-bit options.

For IT departments, the move to 64-bit Windows will be simple, Microsoft officials promise. "Thirty-two-bit applications run without change, so it's an easy transition," Allchin says. The systems-management tools already in place at most companies will manage mixed environments of 32-bit and 64-bit Windows systems and applications, company officials add.

But planning and testing are needed, and everything won't necessarily work. Windows XP x64 won't support DOS, 16-bit, or Posix applications, or some older networking protocols. Jeff Price, senior director of Windows server product management, says IT departments will want to check existing applications for compatibility, performance, and reliability on Windows x64 before deploying new 64-bit servers. Microsoft already knows that certain applications--those with 32-bit, kernel-mode components such as device drivers--will need to be tweaked to run on Windows x64.

That gets to one of Gates' goals at WinHEC--inspire the industry to take on the work that remains to be done. Gates will urge the audience of hardware engineers to develop the device drivers needed to make sure that a variety of computer peripherals can plug and play with Windows x64. "You can mix 32-bit applications and 64-bit applications, but you need 64-bit device drivers," he says. "During the next 12 months, there will be a lot of focus on that."

Application software needs to be developed, too. More than 400 server applications are being readied for Windows x64, including Citrix Systems' MetaFrame, IBM's DB2, Oracle's 10g database and E-Business Suite, and SAP's R/3 and mySAP. Microsoft's own road map calls for 64-bit versions of SQL Server 2005, Visual Studio 2005, Services For Unix, BizTalk Server 2006, and Host Integration Server 2005 this year. The goal is to create 64-bit editions of most of the company's major server applications as they go through their normal release cycle.

Still, it could be several years before Microsoft and its partners get all that 64-bit development work done. "There will be some time, like five or six years from now, where a lot of application updates will start to be 64-bit only," Gates says. "But that's quite some time off."

Gates brings a long-term perspective to these things. It was nearly 20 years ago that Microsoft released Windows 1.0, the 16-bit operating system that started it all. "Windows 1.0 wasn't exactly a barn burner," he says with a laugh. Years later, Microsoft rebuilt Windows in the form of 32-bit Windows NT. "Now," says the software architect, "we're starting some of those same things."

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