Microsoft is reportedly trying to adapt Windows Server for energy efficient CPUs designed by British chipmaker ARM Holdings.

Sources familiar with the matter told Bloomberg the company has created a working software prototype, but it hasn’t decided whether to make it commercially available.

If it did, the move could damage Microsoft’s long-standing relationship with Intel, which promotes competing x86 architecture.

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Chips designed by ARM have revolutionized mobile computing, and are widely predicted to become an important part of ‘hyperscale’ data centers of the future. These CPUs and SoCs are based on reduced instruction set computing (RISC) architecture.

They offer less computational power per core, but are cheaper to make, more energy efficient and don’t require cooling. Other examples of RISC processors include IBM’s POWER family and Oracle’s SPARC.

According to Web Technology Surveys, around a third of all servers run Windows software, so a compatible version could boost the adoption of ARM silicon in the data center.

But even though the idea of dense ARM-based systems sounds attractive, traditional hardware vendors have been reluctant to experiment with this technology.

Earlier this year, HP became one of the first to take the plunge with aptly named Moonshot, a server system built around dozens of cartridges loaded with either ARM or low power Xeon E3 CPUs. It says the ARM version can deliver four times more density and twice the memory than a typical rack for the same performance, power and cooling.

Dell has said repeatedly it is considering a similar approach, and even launched a proof-of-concept in February, but actual products are yet to be announced.

AMD’s first ARM-based 64-bit chip, the Opteron A1100 (codenamed ‘Seattle’), started shipping to developers and early adopters at the end of July.

Microsoft has had a patchy relationship with ARM: on one hand, it sells the moderately successful range of ARM-based Nokia Lumia (soon to become simply ‘Lumia’) smartphones running Windows Phone OS.

On the other, the company’s attempt to adapt a version of Windows 8 for a different architecture as Windows RT failed miserably. The tablet OS suffered from confusing marketing and compatibility issues. A total of seven Windows RT devices were released since 2012, three of them made by Microsoft or its subsidiaries. No further devices have been announced, and the future of the platform is unclear.