Microsoft is making available on April 19 its third “Redstone 3” test build for PC users and another new test build for Windows 10 Mobile users.

The test build for Fast Ring Insiders for PCs is build 16179. The test build for Fast Ring Mobile testers is 15205. The Mobile build is neither fish nor fowl: It’s not a test build for Windows 10 Creators Update and it’s not a test build for Redstone 3. (It’s called “Feature2,” and is a splinter branch that seems destined to continue to be updated for the forseeable future, but not updated to Redstone 3.)

As with the previous two Redstone 3 builds, Build 16179 is light on visible new features and is mostly focused on some of the under-the-covers plumbing. It does, however, include the Power Throttling CPU-power consumption feature that Microsoft introduced for the first time in a widescale way last week. Power Throttling only works on PCs with Skylake or Kaby Lake at this point.

Build 16179 also includes a new feature called Revert VM, which provides automatic checkpoints enabling developers to more easily undo mistakes in their virtual machines.

Beyond that, Build 16179 and Build 15205 include a bunch of bug fixes. The PC build fixes some Desktop Bridge-related issues, and makes the Group Policy for disabling the lock screen available for Windows 10 Pro users. The Mobile test build fixes some Continuum, Edge and Upgrade Advisor issues.

As usual, both of today’s builds include a number of known issues, which testers should read through before installing either build.

Redstone 3 is expected to be generally available later this Fall. Microsoft has yet to disclose what will happen with Windows 10 Mobile beyond the Creators Update; hopefully this information will be shared at Build 2017 in mid-May.