Microsoft Surface RT & Pro estimated to have sold 1.5M units total

Of that 1.5 million, the Surface RT, launched in October, accounts for 1.1 million, Bloomberg reporter Dina Bass tweeted on Thursday. Surface RT is meant, along with other Windows RT tablets, to be a lower-cost alternative to Apple's iPad, which moved 23 million units last quarter.

The Surface Pro, which runs a full version of Windows 8 and is compatible with legacy Windows applications, has moved just under half a million units in the weeks since its January launch. Microsoft markets the Surface Pro as more of a laptop replacement than a consumer tablet, and it is priced accordingly.

When the software giant introduced its first major foray into computing hardware last summer, a number of its hardware partners were less than thrilled at the prospect of having to compete with the company that supplies them with an operating system. Microsoft attempted to assuage OEM fears by assuring them that the Surface was meant more to demonstrate potential form factors that they could emulate, not as the opening salvo of a hardware struggle.

Since introducing the tablets, though, the company has expanded the team working on Surface hardware, with job listings hinting at a next generation of the device. There have also been rumors that Microsoft is working on a 7-inch version of the device to compete with the iPad mini. That version, according to some reports, may feature connectivity with Microsoft's successful Xbox 360 video game console.

No matter the sales of its Surface devices — which are said to be at or near the top among Windows 8 computers — it appears that Microsoft is not looking to exit the hardware segment any time soon. Company representatives have revealed previously that the company will keep trying to market the tablets until they find a winning strategy.