Windows 9 preview is expected to arrive on September 30. The preview release will be a huge step forward for Microsoft Corporation (NASDAQ:MSFT), fixing most of the mistakes the company made with Windows 8. The beta version of Windows 9 will work only on desktops and tablets built around the x86 processors. That means Windows RT tablets except Surface Pro 3 are going to be left out of the fun.

windows 9

Windows 9 to fix the blunder Microsoft committed with Windows 8

That’s because Microsoft has a different plan for them. According to Mary Jo Foley of ZDNet, the ARM-based Windows 9, which will work on Surface Pro 2 and other tablets and Windows Phone, will ditch the desktop entirely. It will offer a glimpse of Microsoft’s “Universal Windows” concept, says Brad Chacos of PCWorld.

It makes sense. ARM-based Windows devices are limited to tablets and phones, not PCs. According to WinBeta, Windows 9 for ARM devices will be for tablets and smartphones, unifying the software giant’s mobile UIs. Rumors of Windows Phone and Windows RT have been doing rounds for months. Last year, the Redmond-based company said that it was working to unify the Windows Phone store and Windows Store.

Windows 8 forced a single interface across different form factors with varied use cases. The new OS will let a tablet be a tablet and a PC be a PC. There will be no middle ground. Your device either has a desktop interface or a Modern UI. That doesn’t mean Microsoft is going to ditch the apps on the desktop. You’ll still be able to use Metro apps in desktop windows.

Windows 9 preview for ARM will come early next year

What about Surface Pro and two-in-one devices? Mary Jo Foley says that the desktop SKU of Windows 9 will support switching between the Windowed mode and Metro mode, based on whether keyboard is connected to your device. The ARM-based SKU of Threshold will work on ARM-based Windows tablets, Windows Phones and Intel Atom-based tablets.

Microsoft will release Windows 9 preview for devices based on x86 processors, not the ARM ones. Foley says Windows 9 preview for ARM devices will be unveiled in January or February 2015.