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.

	Dixon Ticonderoga won't be a first adopter, VP and CIO Grainger says. Photo by Sacha Lecca

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."