Microsoft is ending its support for Intel's Itanium processor with the current version of its Windows Server OS, according to a Microsoft blog posting Friday.

"Windows Server 2008 R2 will be the last version of Windows Server to support the Intel Itanium architecture," Dan Reger , a Microsoft senior technical product manager, wrote on the Windows Server Division Weblog. "SQL Server 2008 R2 and Visual Studio 2010 are also the last versions to support Itanium."

The news will come as a setback for Intel, which has struggled to get its 64-bit Itanium processors more widely used by server makers. It released the latest, quad-core version of Itanium in February after several delays. By that time Red Hat had already announced in January that it would not support Itanium with the next release of its Linux OS distribution.

Burton Group analyst Nik Simpson said it was "no coincidence" that Microsoft announced its decision during the same week that Intel released its powerful new multicore Xeon 7500 series processors, which include high-end reliability features that Intel once reserved for Itanium.

"For Microsoft, reliability was the only thing that Itanium had going for it, the number of Windows licenses sold on Itanium is negligible compared to the x64 business. So the decision to drop Itanium was probably a relatively easy one," Simpson wrote in a blog post.

Microsoft's Reger said much the same. "The natural evolution of the x86 64-bit ('x64') architecture has led to the creation of processors and servers which deliver the scalability and reliability needed for today's 'mission-critical' workloads," he wrote.

Microsoft will continue to provide mainstream support for Itanium-based systems until July 2013, and extended support until July 2018, Reger said, in line with its standard support policy.

Intel recently committed to delivering at least two more generations of Itanium during the next four years, dubbed Poulson and Kittson. HP, which made a big bet on Itanium when it ended the development of its own PA-RISC processor, has repeatedly said that it is committed to Itanium's future.

But the end of support by Microsoft is sure to spark a fresh round of questions about the platform's prospects.

For Itanium, Microsoft's move is "bad, but not disastrous, at least for now," Thompson said.

Most Itanium processors are sold in servers running Hewlett-Packard's Unix variant, HP-UX, he noted. But there will soon be just a handful of OSes remaining for Itanium that have "enterprise-ready credentials," he wrote. Those include Novell's Suse Enterprise Linux (SEL), Groupe Bull's GCOS, and HP's HP-UX and OpenVMS.

"Of those operating system platforms, only HP-UX and OpenVMS actually require Itanium. GCOS and SEL are both supported on x64 processors, which will probably hasten the end of support on Itanium now that x64 can match Itanium for reliability," Thompson wrote.

"So HP is likely to be the last man standing in the Itanium systems business, but the new features and scalability of the 75xx Xeon beg the question, 'will HP adapt its Itanium hardware to support the Xeon 75xx and port HP-UX or OpenVMS to the x64 platform?'"

A Microsoft spokesman confirmed the company's blog post is accurate. Intel could not immediately be reached for comment Sunday.