Windows for Opteron beta doesn't support Nocona

IDG News Service |  Operating Systems

Customers can now purchase workstations using Intel Corp.'s Nocona Xeon processor, with 64-bit extensions to the x86 instruction set, but they can't run the beta 64-bit version of Windows designed for those extensions on the new workstations.

The publicly available beta version of Windows XP 64-Bit Edition for 64-Bit Extended Systems can only be installed on systems with Advanced Micro Devices Inc.'s (AMD's) Opteron and Athlon 64 processors, according to a Microsoft spokesman. During the operating system installation process, Windows checks to see whether or not it is being installed on an AMD system. If it is not, the software cannot be installed, the spokesman said.

Microsoft's developers "essentially required the AMD chips to work with the operating system, just simply because they hadn't tested with any other chips," he said. Independent hardware reviewer Andrew Miller highlighted the incompatibilties in his review of a new Nocona workstation at his Web site (, one of a very few Nocona reviews to make it onto the Web following the chip's release last week.

The public beta for 64-bit Extended Systems was released in September 2003, before Intel had announced its plans to release the Nocona core.It has not been updated since then, and Microsoft's engineers wanted to ensure the beta operating system provided the same customer experience on Intel's chip as it does for AMD's chip before certifying it for Intel's chips.

There are some small differences between the instruction sets used in the two chips. Intel, for example, does not support AMD's 3DNow graphics instructions. Intel uses hyperthreading technology in its Xeon processors, but AMD does not.

AMD also uses two instructions designed to improve Opteron's ability to quickly switch back and forth between applications. The additional instructions were added after AMD published its design papers that Intel used to create the architecture for the Nocona chip. The instructions don't increase performance to any significant degree that most users would notice, according to analysts.

Aside from a few discrepancies, the chips are largely compatible. But even if they use the same instruction set, the chips don't have to use the same method to tell the operating system what instructions are available, said Kevin Krewell, editor in chief of the Microprocessor Report in San Jose, California.

For example, AMD's and Intel's 32-bit chips are compatible, but don't necessarily use the same code to let the operating system know what types of instructions are available, Krewell said. Right now, the beta version of the operating system is probably tuned to recognize only AMD's method of identifying its instructions, but it will be relatively easy for Microsoft to add support for Intel's code, he said.

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