Microsoft warned PC partners it was entering tablet hardware space

Microsoft on Monday held an event to show off its upcoming Windows 8 tablet. The Surface will launch first with an ARM version, with a Pro model running Intel chips to arrive several months later. Though the device's announcement has generated plenty of interest, some pundits have called the tablet "vaporware" because Microsoft neglected to reveal specific details on the pricing, battery life and the release date.

All Things D's Ina Fried interviewed Ballmer after Microsoft's media event on Monday to learn more about the company's plans. Though Ballmer was predictably tight-lipped about the project, he did reveal that Microsoft vendors knew about the Surface tablet prior to the unveiling.

"Our PC partners knew in advance we were announcing something today in this space,” he said.

When asked how they felt about it, Ballmer simply replied with "no comment."

Microsoft is walking a fine marketing line between touting its new hardware while supporting its partners. For instance, Ballmer noted during his interview that most PCs sold next year will be from other companies, while also hedging that Microsoft could see significant sales of the Surface.

“If you look at the bulk of the 375 million machines that get sold (next year), they probably aren’t going to be Surfaces,” the executive said. “On the other hand, we could have a sizeable business.”

Ballmer called the Surface an "important companion" to the "Windows 8 story," but he softened the statement by adding that it's "not the only piece."

The executive also revealed details on how Microsoft worked to keep the project under wraps. Information about the Surface was apparently only provided to a small number of Microsoft employees. Ballmer himself elected not to regularly use a prototype because of his frequent public appearances.

With the Surface, Microsoft will join Google in challenging Apple at its own game. Third-party hardware vendors have had trouble catching the iPad, leaving operating system makers to take matters into their own hands. Google chairman Eric Schmidt said late last year that his company would release a "tablet of the highest quality" by June. Assuming that such a device has remained on schedule, the company could unveil it at its Google I/O conference in late June. Google also bought its way into the hardware business with its recent $12.5 billion acquisition of Motorola Mobility.

According to one recent market analysis, Apple will take back some of its market share from Android tablets this year. IDC expects the iPad to achieve 62.5 percent of global tablet sales, up from an estimated 58.2 percent last year.