Four months after the first release of Android 5.0 Lollipop, Google has followed up with a second version: Android 5.1. The speedy turnaround time compared to Android 5.0 (which appeared a year after 4.4) means that there aren't many large-scale changes to look at—but the release does feature numerous little improvements and tweaks.

It’s faster! (on the Nexus 6, at least)

Ron Amadeo

Ron Amadeo

Ron Amadeo

5.1 seems to have eliminated many of the performance issues with the Nexus 6. When we initially reviewed the device, the Nexus 6 was slower at loading apps and switching tasks than the older Nexus 5 had been. With 5.1, the newer phone feels much snappier; with non-game apps, it can now keep pace with the Nexus 5.

On benchmarks, we're seeing much higher random read and write scores on the Nexus 6 with 5.1; random read gets a 2x speed boost, while random write is a whopping 9x faster. The same dramatic speed boosts aren't present on the Nexus 5, and we suspect the difference is that the Nexus 6 is encrypted while the Nexus 5 is not. According to Francisco Franco, a longtime third-party Android kernel developer, Google is now using NEON instructions on the Nexus 6 to speed up encryption performance. Performance could be further improved by enabling hardware-accelerated encryption, which the Nexus 6 still doesn't use, but Google has been experimenting with the feature in the Android Open Source Project.

Google also changed the way the Nexus 6 CPU works. In Android 5.0, when the device was idle with the screen on, two of the Nexus 6 CPU cores would shut down. 5.1 runs in quad-core mode all the time. Theoretically, this setup uses more battery power, but the majority of device power usage is consumed by the screen, not the CPU.

Device Protection

Ron Amadeo

Ron Amadeo

Device Protection is the biggest new feature of 5.1. Android has had security features like remote location, remote locking and erasing, and secure lockscreens for years, but if a thief only wants to steal your hardware, wiping the device would bypass all of those protections. Device Protection now allows you to nuke the device remotely but also keep the password in place, making the phone useless unless the new user knows the old account name and password. Device Protection also kicks in if the device is wiped through fastboot or other developer tools. The feature is roughly equivalent to the Activation Lock feature that Apple introduced for all iDevices in iOS 7.

Device Protection isn't enabled by the user; it automatically turns on when you set a secure lock screen (PIN, Pattern, or Password). It can also be remotely enabled by locking the phone through the Android Device Manager. After a protected phone is wiped, a new screen pops up during the setup process asking for the e-mail and password of an account previously used on the phone—no account, no access. Pass the verification and you proceed to device sign-in like normal. (Of course, all bets are off if your device is rooted or you have an unlocked bootloader.)

It's unclear what older devices will get Device Protection. All new devices that ship with 5.1 will have it, but devices that get the new OS as an upgrade might not get the new feature. In our limited testing, for instance, the Nexus 6 and 9 have Device Protection, but the Nexus 5 does not.

Other small changes

Ron Amadeo

Ron Amadeo

Ron Amadeo

Ron Amadeo

Ron Amadeo

Ron Amadeo

Ron Amadeo

Ron Amadeo

Ron Amadeo

Ron Amadeo

Ron Amadeo



Ron Amadeo

Ron Amadeo

Ron Amadeo

Ron Amadeo

Ron Amadeo

Ron Amadeo

Ron Amadeo

5.1 also makes many small interface changes, documented in the gallery above. Notification and volume controls have seen improvement, and the OS has been tweaked and polished all over.

In addition, 5.1 brings built-in support for dual SIMs (previously something OEMs had to add) and HD Voice support.

Android 5.1 is one of the smaller minor version Android updates, down there with versions 4.2 and 4.3. But it brings a few nice changes and thankfully seems to solve many of the Nexus 6 performance problems.