Microsoft made two different test versions of Windows available on December 10. There is a version of Dev Channel 21277 of the pre-release branch that includes app emulation for Arm x64, among other features. And there is another Windows 10 test release, # 20277, available for Iron (Fe) branch Dev Channel testers.
RS_Prerelease build 21277 – which should eventually be referred to as the “Cobalt” branch – includes features that Microsoft has already tested but which were phased out at the end of October. These include the updated emoticon picker, redesigned touch keyboard, voice typing, and more. It also provides the Arm emulation support mentioned above.
Currently, Windows on Arm natively supports Arm applications, including ARM64 versions. But so far only 32-bit Intel (x86) applications are supported in emulation. This lack of x64 emulation has limited the number of apps that can run on Windows on Arm devices, since 64-bit apps were only available on Windows on Arm (WoA) devices, if the developers created them. native versions. At present, these Arm x64 applications can also be run in emulation.
Pay attention to the fine print
More details on the Arm x64 emulation preview feature can be found in this Microsoft post.
The Iron release (20277) also contains fixes to several known issues. The pre-release includes a set of new features and updates.
Before Insider Program members rush to install RS_Prerelease build 20277 branch, they need to read the fine print. These versions are currently offered as optional updates for “researchers”, which means that Insiders will have to choose to install them. Once they do, they won’t be able to come back to Iron; they will continue to receive RS-Prerelease builds in the future.
What updates in the coming weeks?
Those who don’t want to do this can continue to automatically get builds from the Iron branch until Microsoft moves all Insiders from the Dev chain to RS-Prerelease builds “sometime after the holiday break” .
Microsoft officials have still not said publicly whether there will be a feature update for Windows 10 in 21H1, and whether that update will come from the Iron branch. Unofficially, we know that 21H1 will be a very small update (in terms of functionality), and that it will take place next spring. The 21H2 / Cobalt version is shaping up to be a bigger and more feature-rich version, according to some sources.