Microsoft has launched the first general public beta for its Windows Server 2003 64-bit operating system designed for AMD's Opteron chip.

The Windows Server 2003 64-bit Extended System preview is available only in the Enterprise Edition, planned for general availability in the second half of 2004 along with a Standard Edition. A Datacenter version is not in the works given that no hardware manufacturer has committed to developing a system that would tune the operating system for a specific hardware platform, which is the way Datacenter is sold.

Microsoft has been working with AMD for nearly two years to develop the 64-bit operating system for its chips: Athlon on the desktop and Opteron on the server. The 64-bit platform processes more data per clock cycle, allows greater access to memory, and speeds numeric calculations.

Similar 64-bit operating systems have been available on the Unix platform for years and Microsoft is playing catch-up.

Last April the software giant released a 64-bit version of Windows Server 2003 for the Intel architecture and then promised to follow it up with support for AMD’s chips. Last fall, Microsoft unveiled the first private beta of the Opteron-tuned software, which uses 64-bit extensions to the x86 instruction set to allow users to run both 32-bit and 64-bit applications natively on the same chip.

That is in contrast to Intel’s Itanium, which runs 32-bit applications in emulation mode.

“It appears that the Intel architecture has some performance issues when trying to run 32-bit code,” says Dan Kusnetzky, an analyst with IDC. “AMD kept the 32-bit core and wrapped the 64-bit support around it.”

Kusnetzky says the performance differences may be significant since 32-bit code is the mainstay of Windows-based applications and many vendors and companies may be unwilling to rewrite their code in the near term.

“We are excited about the AMD architecture in particular because our install base of customers has a lot of 32-bit apps,” says John Borozan, Microsoft product manager for 64-bit Windows Server. “You can double the amount of memory available to an application without having to modify it so the AMD architecture provides a smoother migration path.”

But Borozan says it is hard to make an apples-to-apples comparison of the AMD and Intel chip architectures.

Despite the 32-bit features of the AMD chip, Microsoft is warning users that the AMD optimised platform is incompatible with 32-bit applications that have 16-bit installers such as SQL Server 2000 SP3; applications that depend on the current version of the .Net framework and applications that have 32-bit kernel-mode drivers such as Exchange 2003.

Only a few 64-bit applications are compatible with the beta, according to Microsoft, including Computer Associates eTrust Anti-Virus beta for AMD 64-bit and Microsoft’s own SQL Server "Yukon" beta.

The 32-bit applications that are compatible include IBM DB2 Enterprise Edition 7.2, IBM WebSphere Application Server, Lotus Domino Server 6.0, J.D. Edwards ERP 8.0 and SAP R/3 4.7.

The general release of the 64-bit Windows Server code for Opteron is the same code released to private testers last fall. Microsoft officials say the OS is not feature complete and updates to the beta will be made available although there may not be another formal beta before final release.

Microsoft says Windows Server 2003, Enterprise Edition, for 64-Bit Extended Systems is only compatible with the AMD chip and will not install on Itanium-based systems. The beta can be installed on up to 10 computers. Microsoft also is creating a private newsgroup for beta testers to discuss technical issues.

Microsoft says the Enterprise Edition beta is well suited for large databases and line-of-business applications. It can support up to eight processors and 64GB of RAM.

The Standard Edition is targeted at high-performance computing clusters, Terminal Services and Active Directory data stores larger than 2GB. It supports up to four processors and 32GB of RAM.