Microsoft on Tuesday launched a beta version of its Windows XP operating system that supports AMD's new 64-bit Athlon on the desktop and the chipmaker's Opteron 64-bit processor on workstations and servers. A final version will be released in the first half of 2004, Microsoft said.

The new version of Windows, which goes by the extended moniker of Windows XP 64-Bit Edition for 64-Bit Extended Systems, isn't the first XP to tackle 64-bits. Microsoft has long made available a version of Windows XP for Intel's 64-bit processors.

Microsoft has dubbed the new technology Windows on Windows 64 (WOW64), and said that taking XP into the AMD 64-bit universe would let customers who currently have Windows XP-compatible 32-bit applications--such as Office XP or Office 2003--run those apps on a 64-bit operating system.

"Until now, the inability to efficiently run 32-bit applications on 64-bit systems has been a major barrier to investing in 64-bit technologies," said Chris Jones, VP of Microsoft's Windows division. "Customers will be able to run both 32-bit and 64-bit applications on a single platform."

AMD, which debuted its 64-bit Athlon processor for the desktop on Tuesday, is taking a different tack on 64-bit than its prime competitor, Intel. AMD touts 64-bit for desktop PCs, relies on the Athlon's ability to run 32-bit applications without the performance degradation of an emulator, and boasts that when native 64-bit operating systems and apps become available, users will be able to migrate without having to make another investment in hardware. Intel, meanwhile, has repeatedly said that 64-bit belongs on servers and workstations, and that there's no need for businesses to invest in 64-bit processors, software, and operating systems for the traditional desktop.

According to both AMD and Microsoft, one of the barriers to 32-bit processing is its current 4-Gbyte memory limit. The Athlon, when paired with a 64-bit operating system, will allow PCs with more than 4 Gbytes of RAM.

One analyst sees that argument, and arguments in general for 64-bit on the desktop, as beside the point for now.

"I don't think this is a very big deal," said Michael Cherry, an analyst with Directions on Microsoft. "People seem to be able to do what they need to do with 32-bit processing."

He noted that while moving to 64-bit processors is inevitable--"we'll probably all have 64-bit machines on our desktops in a couple of years"--there are lots of other ways that companies can see performance improvements without investing in new processors.

In fact, Cherry recommended that rather than spend money on 64-bit desktops, companies should profile their operations to actually determine if they have performance bottlenecks, and if so, where they are.

"I don't think 64-bit processing--and operating systems--will be the better investment, at least initially," he said. He urged companies to do their homework to determine whether investing in, say, multiple processors might not be smarter than spending on boosting processor width.

Cherry also had a cynical explanation for the reason behind Microsoft's move to support its partner AMD into 64-bit. "All three of these companies--Intel, AMD, and Microsoft--like it when there's a change in processors, because when there is, users buy new hardware, new operating systems, and new software.

"That's the whole angle," he said. "There's no other demand driving this."

The beta of Windows XP 64-Bit Edition for 64-Bit Extended Systems is available now to subscribers of the Microsoft Developer Network; Microsoft says it will release in final form during the first half of next year.

Also on Monday, Microsoft launched the beta of Windows Server 2003 for 64-Bit Extended Systems. Like its XP sibling, the server software written for the AMD line of 64-bit processors is scheduled to ship in the first half of 2004.