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.

But software would need to be written to support the 64-bit ARM instruction set, and porting many x86 64-bit applications is a challenge, King said. Existing applications that ran on previous versions of Windows do not run on RT.

"From a purely technical perspective, porting many common x86 applications to ARM is problematic," King said.