But that carries some risk, and not only in the delays that make Microsoft fall even further behind Apple's iOS and Google's Android.

"They could end up outrunning the hardware that it's meant to run on," said Cherry, if Intel isn't able to produce chips competitive on battery life with ARM. Cherry cited Windows Vista -- Microsoft's 2007 operating system failure -- as an example of the same phenomenon, when the OS required more than the then-current hardware was able to provide.

"It's going to be some time before Intel's SoC [system-on-a-chip] is up to the same battery life as ARM," Cherry said.

Microsoft has not yet disclosed a release date for either Windows RT or Windows 8, or said when devices running the former will go on sale. Yesterday, a Microsoft executive said only that development of both operating systems was "on our schedule," but did not say what that schedule was.

Most analysts expect Windows 8 to launch in the fourth quarter, perhaps in October, which would give computer makers the chance to sell new PCs and devices during the holidays.