Microsoft Wednesday announced it will release a 64-bit version of Windows Server 2003 and Windows XP for Advanced Micro Devices' forthcoming Opteron and Athlon64 processors.Microsoft\u00a0will release a 64-bit version of Windows Server 2003 and Windows XP for AMD's forthcoming Opteron and Athlon64 processors, Microsoft announced Wednesday.Microsoft announced support for AMD processors last year, but the omission of support for AMD in the release-to-manufacture (RTM) version of Windows Server 2003 unveiled last week led observers to wonder if Microsoft would follow through on its plans. Beta releases of the operating systems for the AMD chips are expected in the middle of 2003, Microsoft said in a press release."This is a milestone for our customers, and our hardware and software partners. They can now test and develop on beta 64-bit versions of Windows Server 2003 (for Opteron), and Windows XP for the Athlon64 processor," said Brenda Forsythe, an AMD spokeswoman.Later this month, both AMD and Microsoft will launch their next-generation server products. Microsoft is set to unveil Windows Server 2003 on April 24, two days after AMD releases the Opteron. The Athlon64 for desktop PCs is expected to be released in September.Windows support for Opteron will not be available at the launch of either product. The beta releases scheduled for the middle of the year indicate that a production version of both operating systems will ship around the end of the year, said Gordon Haff, an analyst with Illuminata in Nashua, N.H.Microsoft is looking at when it will release the production versions,\u00a0said Dave Ciuba, senior product manager at Microsoft.Microsoft's lack of specific details regarding support for the AMD chips had caused a lot of hand-wringing among AMD enthusiasts. "There's a big difference between a public statement of support and various rumors of when things are going to be available, and Microsoft actually putting out a release saying, 'Here's our plan,'" Haff said.The news that a production version of Windows XP will be available so quickly after the launch of the Athlon64 is significant, said Nathan Brookwood, principal analyst for market research company Insight 64 in Saratoga, Calif."The server version was never in doubt. But the desktop version, they had been a little more coy about that," Brookwood said."Seeing both releases in the same time frame is a positive for AMD. It took almost 10 years for Microsoft to release 32-bit support (Windows 95) for Intel's 32-bit chips. This time, it will only be about three months," he said.AMD's processors will use the x86-64 instruction set, which adds 64-bit extensions to the x86 instruction set used in 32-bit processors from AMD and Intel. Users will be able to run both 32-bit and 64-bit applications on the chip, but will need to recompile their existing 32-bit applications to take advantage of the benefits of 64-bit computing. Users will still see a performance benefit on 32-bit applications over existing AMD server processors, the Sunnyvale, Calif., company claims.Most versions of Windows operating systems are written for the 32-bit x86 processor, so Microsoft needed to recode the operating system for Opteron or Athlon64 for IT managers that want to run Windows on computers with either chip.Both the 64-bit client and server versions of Windows for the AMD processors use the same compiler, so Microsoft was able to use much of the same code in bringing both Windows Server 2003 and Windows XP to the x86-64 instruction set, Ciuba said.Last year, Microsoft released a 64-bit version of Windows Advanced Server for Intel's Itanium 2 processor, and included support for Itanium in the RTM version of Windows Server 2003. Itanium uses an entirely new instruction set developed by Intel\u00a0called EPIC (explicitly parallel instruction computing). It can run x86 32-bit applications, but in a much slower compatibility mode than applications recompiled for the 64-bit EPIC architecture, Haff said.Both Intel and AMD are still far behind their Unix competitors in the data center, such as Sun\u00a0and IBM, which use 64-bit RISC (reduced instruction set computing) chips for corporate applications. Intel's Itanium has had trouble getting off the ground, with support from only one major vendor, HP."Intel has had a 64-bit Windows chip primarily in name only. Just now there has been a real production version of Windows for it, and it hasn't gotten widely deployed," Haff said. Most users who have chosen Itanium 2 platforms have opted for Linux operating systems, he said.Right now, it's a toss-up as to which processor will be preferred by Windows users, Haff said."Intel has advantages as a company, and Itanium has some good, demonstrated performance benefits. But the Opteron's compatibility with 32-bit Windows binaries at full speed, rather than having to recompile new versions of all your applications, is attractive," he said.