Microsoft could be looking to revive one of its biggest failed experiments
ARM differs from Intel in how the chipset is designed and, as such, cannot support applications designed to run on an Intel-powered machine (described as either x32 or x86).
Microsoft originally made two versions of the Surface: An Intel-powered version (known as the Pro) and an ARM-powered version (known as the RT). The latter was later killed.
It's unclear why Microsoft is experimenting with ARM-based technology in Windows 10, but one reason could be to work out how to ship another Surface device that contains a non-Intel CPU.
One theory, put forward by Petri, is that Microsoft could be building an ARM-based version of Windows Server, the software that is used to power larger-scale server computers.
The benefit of ARM over Intel is efficiency, both in terms of space and power. Mobile devices often use ARM-based chips over Intel because they use less powerful and take up less space.
Petri notes that Microsoft hired someone to build a way of making Intel-based applications run on an ARM machine. One of the core criticisms of the Surface RT was that it didn't run Windows 7 apps, and this software could solve that issue.