Microsoft has announced, through a recent entry on its official blog site, that it has started seeding Windows 10 Mobile update to supported smartphones that are currently running on Windows 8.1.
The Lumia smartphones that are expected to receive the Windows 10 Mobile update include the Lumia 430, 435, 532, 535, 540, 635 1GB, 636 1GB, 638 1GB, 640, 640 XL, 730, 735, 930 and 1520. Some non-Lumia devices, like the BLU Win HD w510u, BLU Win HD LTE x150q, and the MCJ Madosma Q501 will also be upgraded to the latest version of Microsoft mobile operating system.
Most of the low-end Lumia smartphones, particularly those with only 512MB of RAM, along with some notable handsets like the Lumia 1020 , 930, and 920 are not included on the list of devices that will get the update.
Based on their internal testing, as well as the feedback from users who have tried the beta version of Windows 10 Mobile, the update has caused a decrease in performance on the Lumia smartphones that are not on the list. Hence, Microsoft decided not to seed the update for the devices that have not met its standards for delivering the best possible experience to the user.