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Butter makes a good Android lubricant
The Nexus 7 features the latest version of Android, version 4.1 Jelly Bean, and the new release is really a big step forward. Its most compelling feature is a series of responsiveness optimizations that fall under the Project Butter umbrella. I don't know where Google comes up with these code names, but slathering jelly beans in butter sounds like something Homer Simpson might do.

Project Butter aims to improve responsiveness in several ways, including the requisite internal latency reductions. More specifically, everything in the OS, from app rendering to touchscreen processing to screen composition, now runs at 60Hz and is synchronized with the refresh rate of the LCD using vsync. Triple buffering has also been implemented to ensure the OS always has a new frame ready for the next display refresh. The end result is a more fluid user interface than Android 4.0, otherwise known as Ice Cream Sandwich.

Don't take our word for it, though. We've managed to capture Project Butter's payoff using a high-speed camera shooting 240 frames per second. In the videos below, you can see the difference between the Nexus 7's UI animations and those of the Transformer and Transformer Pad Infinity, which are both running Ice Cream Sandwich. The first set of videos shows the application screen loading up before we return to the home screen.


Nexus 7


Transformer


Transformer Pad Infinity

Animations don't necessarily execute any quicker on the Nexus than on the Transformers, but the results are much smoother. Even the Infinity, which has a faster Tegra 3 processor, suffers from visible hitching when compared to the Nexus 7. Incidentally, that UI hitching is called "janking" in programmer-speak.

When looking at these videos, keep in mind that the old Transformer uses a dual-core Tegra chip running at just 1GHz. I'm curious to see how much more responsive this older tablet would feel with a Jelly Bean update. Asus has committed to bringing Android 4.1 to the Transformer Pad Infinity, but the original Transformer may be too old to qualify for an upgrade.

Next, we're going to look at Android's multitasking interface. The difference should be easy to spot.


Nexus 7


Transformer


Transformer Pad Infinity

Ice Cream Sandwich exhibits a lot of janking on the Transformers. The Nexus 7 feels as smooth as it looks, and the improved responsiveness permeates the entire user interface. Even the touchscreen seems more responsive. Google has made optimizations there, too.

The most interesting touchscreen tweak is actually a response to the power-saving tech built into modern processors. SoCs like the Tegra 3 reduce the clock speed of their CPU cores during idle periods. To prevent idling processors from slowing the response to user input, Jelly Bean ramps up the CPU clock speed the moment it detects touchscreen contact.

To make touchscreen input feel more natural, the OS tracks touch events based on the anticipated position of one's finger when the screen refreshes. The finger's trajectory is used to determine that position, and the scheme works pretty well in practice. Compared to other Android tablets, the Nexus 7 seems to exhibit less latency when dragging icons around the home screen. We won't be satisfied until the difference is illustrated by more high-speed footage, but there wasn't enough time to make that happen for this review.

We also have plans for high-speed tests against the new iPad, which is the gold standard for tablet responsiveness. My seat-of-the-pants impression is that the Nexus 7's UI is now on par with the iPad, at least in terms of smoothness. Since the tablets have different user interfaces, we're going to have to get creative to come up with meaningful comparisons. Stay tuned.