Customers can now purchase workstations using Intel's Nocona Xeon processor, with 64-bit extensions to the x86 instruction set, but they cannot run the beta 64-bit version of Windows designed for those extensions on the workstations.
The beta version of Windows XP 64-bit Edition for 64-bit Extended Systems can only be installed on systems with Advanced Micro Devices' (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.
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 do not 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 do not 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.
For example, AMD's and Intel's 32-bit chips are compatible, but do not 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 recognise 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.
Microsoft is working on a new public release of the 64-bit beta operating system, the company spokesman said, but customers who have access to Microsoft's Tech Beta program will be able to preview the 64-bit operating system on Intel-based workstations.
A beta version of Windows compatible with Intel's 64-bit extensions technology is expected to be released by the end of next month.
Intel will introduce a server chipset for its Nocona Xeon processors in August, around the same time the new beta version is expected.
Intel and Microsoft have promised that the final versions of both Windows XP and Windows Server 2003 for 64-bit extended systems will run on Xeon and Opteron servers without any hitches. The production version of the operating system is expected in the fourth quarter.
Tom Krazit and Robert McMillan write for IDG News Service