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The Palm Pre’s possible Achilles heel: battery life

There are any number of glitches that could keep the Palm Pre from totally …

The webOS software stack

The Palm Pre application platform is built on Web standards and will allow developers to build software with HTML and JavaScript. Although this provides an enormous amount of functionality, it also means higher resource consumption.

It's true that recent innovations in JavaScript development have significantly boosted execution speed. SquirrelFish Extreme, for example, uses sophisticated caching techniques and JIT compilation to achieve excellent runtime performance. Unfortunately, the SquirrelFish JIT engine is only available on the x86 architecture and does not yet run on mobile phones and other ARM-based devices.

Performing some common operations in JavaScript, such as string concatenation, can be a lot more computationally intensive than doing it with native code. On top of that, programs that are built with Web-based technologies are going to rely on DOM manipulation to control the user interface, which will take more processing power than using a conventional native widget toolkit.

Web runtimes are increasingly viewed as a more portable alternative to native development, and there are some emerging standards and existing mobile implementations that show a lot of potential in this area, but the technology is extremely resource-intensive; it doesn't really scale well enough to be used pervasively on conventional handsets. The Pre's Cortex A8 will certainly help make the software environment fit into a mobile, but the combination of the processor and the software stack could make for a big drain on battery life.

The real performance and power impact of the Pre's web-oriented development approach is still difficult to guess because we can only speculate about how it will work. It seems like a safe guess that it's going to be WebKit-based, because we now that the Pre is using a WebKit-based browser. But if the application layer is using Gecko, it would change the equation a bit, because Gecko's TraceMonkey JavaScript interpreter already has preliminary support for ARM JIT compilation thanks to a collaborative effort with Adobe. It could also be using something completely different, like some kind of AOT compiler.

Synergy is probably chatterific

The Synergy approach to managing user data, which I described in an earlier article after the webOS unveiling, implies that the Pre is fairly chatty on the network. If that turns out to be true then this factor alone could dwarf the processor's contribution to the overall system power draw.

Think about it. If you're using GTalk, IMAP, Exchange ActiveSync, and a bunch of other cloud-based services, all of which are supposed to be "live" on the phone, that's a lot of different transports either polling or being pushed at different times over the network. That's also a lot of different TCP/IP connections being opened and closed, and a lot of very power-hungry CDMA radio activity.

(In a discussion thread in the Mobile Computing Outpost where I originally ran this "Synergy == battery drainage" by our users, there was some useful discussion of how Blackberry solves a very similar problem with push e-mail. A number of users noted that RIM doesn't actually use a TCP/IP connection over the data network to get email; rather, e-mail is allegedly pushed through the cell network's control channel, which makes it much less power-intensive than a regular data connection.)

Are Pre users destined to carry replacement batteries?

In the end, efforts like this one to think about the Pre in terms of potential battery life are of necessity just educated guesswork. There are way too many questions about the hardware and software that are yet unanswered, and by the time most of them are answered we'll probably be close to launch.

So while I'm not willing to proclaim that Pre's battery life will definitely stink, I do think that there's good reason to believe that it will be short enough that many users will find it unsatisfactory. But even then, as any veteran of the online discussions around the iPhone 3G's battery will tell you, "unsatisfactory battery life" is in the eye of the beholder.

Ryan Paul contributed to this report

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