A day after making its first Windows 10 20H2 test build available to a group of Windows Insider testers, Microsoft is pushing out its first build from a new test branch to its Dev Channel testers. (Dev Channel testers are those formerly known as Fast Ring and Skip Ahead Ring testers.)

On June 17, Microsoft made available Build 20150 to the Dev Channel. Microsoft officials have said that Fast Ring/Dev Channel builds are not tied to specific upcoming Windows 10 feature releases. In other words, the Dev Channel is testing a bunch of features which may or may not be included in a future Windows 10 feature release. However, today’s test build is the first from the new RS_PRERELEASE branch, which is codenamed “Iron.” Some of the features that are tested as part of this branch will likely end up in Windows 10 21H1, due out in the spring of 2021.

(Windows 10 20H2, which as of yesterday is being tested by Insiders in the Beta channel, is considered part of the “Manganese” wave, for those trying to keep track of codenames at home.)

Like most early Dev Channel/Fast Ring builds, today’s new test build doesn’t include many notable new features. Microsoft will likely add more new features as the team working on “Iron” add them internally between now and December 2020. It does include a number of fixes and updates.

Build 20150 does include three new Windows Subsystem for Linux (WSL) features, however. The three are GPU compute, WSL install and WSL update. GPU compute enables Linux binaries to leverage a user’s GPU, which officials said will be a big draw for those doing machine learning and data science work inside WSL. The WSL install command lets users install WSL with a single command. And WSL update allows users to manage the Linux kernel version used by WSL 2 distributions. 

Microsoft officials said GPU access for WSL2 would be coming a few weeks ago.

Today’s new build also marks the start of Microsoft rolling out the new search box on the default app settings page. Microsoft officials say the search box performance should be improved with this release.