Google has posted the second developer preview of Android 8.1. This release brings a "near final" build of Android 8.1 to the Pixel 2 and 2 XL, the Pixel 1 and 1 XL, the Pixel C tablet, and the Nexus 6P and 5X.
The first Android 8.1 Preview, which launched last month, was a bit of a mess. Google's incremental update files didn't work, and then the company had to take them down. The full system images couldn't be flashed on the Pixel 2 for a few days due to needing a new version of the Android Developer Tools that wasn't yet posted. When we did get the files finally flashed, we found out that the headline feature—enabling Google's custom SoC, the Pixel Visual Core—didn't actually work. After a bit of a back and forth with Google, the company confirmed that the the Visual Core would be enabled in the second preview.
Barring any unforeseen hiccups, this second preview should finally enable the Pixel Visual Core. The custom, Google-designed SoC has been dormant in the Pixel 2 and Pixel 2 XL. The eight core chip will supposedly accelerate Google's HDR processing and enable hardware acceleration for other machine learning tasks. Google apparently envisions all Android phones having special hardware like this, since the Visual Core is the first implementation of Android 8.1's new "Neural Networks API" (NNAPI). The new API allows app developers to write code for special neural net co-processors like the Pixel Visual Core (and to provide a software backup for phones without the special hardware).