Finally, some Windows 8.1 phones are getting Windows 10 Mobile

After much delay, the new Windows mobile OS is available to old Windows phones -- but only some

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Credit: Microsoft

With minimal fanfare, Microsoft began rolling out Windows 10 Mobile as a free upgrade for older phones on Thursday, fulfilling a promise the company began making more than a year ago.

The company's original promise was that "broad availability of Windows 10 on other devices, including mobile phones, would begin rolling out in December" 2015 -- and it's now mid-March.

However, not every Lumia or third-party Windows phone will be eligible for the upgrade from Windows Phone 8.1 to Windows 10 Mobile. There are 18 smartphones on the list of supported phones, including the Nokia/Microsoft Lumia 1520, 930, 640, 640XL, 730, 735, 830, 532, 535, 540, 635 1GB, 636 1GB, 638 1GB, 430, and 435. Also getting the upgrade are the Blu Win HD w510u, Blu Win HD LTE x150q, and MCJ Madosma Q501 smartphones. 

Last summer, Microsoft published a list of 10 Lumia phones that would be eligible for upgrades, all of which made the final cut. 

Noteworthy omissions include the beloved Lumia 1020 as well as the HTC One M8, Microsoft's failed attempt at convincing third-party hardware makers to sell their own smartphones powered by Windows Phone.

[Updated 3/21/16] Also missing from the Windows 10 Mobile support list are the Lumia 920 and 925, smartphones that, like the 1020, ran the Windows 10 Mobile betas. Microsoft said users experienced too many bugs for those models to make the final Windows Mobile 10 cut.

[Updated 3/21/16] Microsoft also said it doesn't expect to make Windows 10 Mobile available for other Windows 8.1 smartphones, even those with sufficient memory and processing speed, with the possible exception of the Lumia Icon. Microsoft said that any Windows 8.1 smartphone with less than 1GB of memory would definitely not get Windows 10 Mobile.

"As Windows 10 delivers significant new innovations, many older devices are not able to successfully upgrade without an impact on the customer experience," Michael Fortin, the corporate vice president responsible for Windows and Devices Group core quality, wrote in a blog post. “Our goal is to only offer the Windows 10 upgrade to devices that we are confident can continue to deliver a good customer experience.”

[Updated 3/21/16] You can manually request the update from your Windows 8.1 smartphone by downloading the Upgrade Advisor app from the Microsoft Store. The app will let you know if your smartphone can be upgraded. If the update is available, it will offer to begin the upgrade. Otherwise, you'll have to wait until your carrier makes the upgrade available, at which point Microsoft says your phone will alert you to the upgrade's availability.

This story, "Finally, some Windows 8.1 phones are getting Windows 10 Mobile" was originally published by PCWorld.