Windows RT is on tablets with 32-bit processors from Nvidia and Qualcomm. Microsoft's Surface and Asus' Vivo Tab RT tablet have Nvidia's quad-core Tegra 3 processor, while Dell's XPS 10 and Samsung's P8510 Ativ Tab have Qualcomm's dual-core Snapdragon S4 processor.

The 32-bit Windows RT OS has a limited memory ceiling, and a 64-bit Windows RT OS would expand the memory capacity in tablets and PCs. A 64-bit version of Windows on ARM would also bring it on par with Windows 8.

Nvidia is developing a processor core based on ARM's 64-bit architecture under the code-name Project Denver. Nvidia declined to comment on development of 64-bit software for Windows.

A Qualcomm spokeswoman said the company cannot comment at this time on specific product plans. However, Qualcomm is an ARM partner and helps explore and evaluate emerging technologies including 64-bit software support, the spokeswoman said in an e-mail.

Microsoft's interest isn't surprising since the move to 64-bit seems like a natural progression for ARM and supporting vendors, just as it was for x86, said Charles King, principal analyst at Pund-IT.