Laptop battery life benchmarks are out of juice

Computerworld - In an industry that gets off on throwing obscure benchmarks at buyers ("pixel fill rate," anyone?), laptop battery life is one of the easiest to understand.

It's also long been one of the least useful, critics charge, due to the industry's deceptive use of the dominant standard, the MobileMark benchmark created by the Business Applications Performance Corp. (BAPCo), an industry consortium whose members include Intel Corp., Dell Inc., Hewlett-Packard Co., Advanced Micro Devices Inc. and others.

"Everyone in the industry knows this benchmark is wildly optimistic and that the actual battery life you'll get is often less than half what MobileMark suggests," wrote analyst Rob Enderle last month. "This is because MobileMark measures battery life much like you might measure gas mileage if you started the car, put it in neutral, and coasted down a long hill."

The latest MobileMark 2007 report measures laptop battery life under three scenarios: reading a document, watching a DVD movie, and doing a "representative" mix of productivity tasks, such as reading and composing documents, editing photos and encoding Flash videos (see page 13 of white paper).

But rather than using an average time based on all three measures, BAPCo designates its third scenario as the way most people use their laptop.

There are several problems with this, according to critics. First, doubters such as AMD say that the productivity test assumes that the notebook is idle 90% or more of the time.

Second, MobileMark's "productivity" scenario assumes that users, when active, are using only software such as Adobe Photoshop or Microsoft Office. They don't test usage of music or video applications such as iTunes or Windows Media Player, games or Web browsing. The test also assumes that Wi-Fi is turned off.

That seems particularly unjustified today, since netbooks are touted as on-the-go, Web-centric devices, or high-definition video-capable machines.

Finally, MobileMark 2007 allows PC vendors to set their laptop screen brightness at the lowest possible setting, provided it is no lower than 60 nits (a nit is a measure of brightness. The problem, again pointed out by AMD, is that 60 nits is quite dim, being only about one-fifth of most notebook PCs' maximum screen brightness.

According to an informal reader poll at Neowin.net, a Windows community site, fewer than 15% of respondents run their notebooks that dim.

BAPCo defended its MobileMark benchmarks. "The content of BAPCo benchmarks are vigorously debated and cooperatively developed by BAPCo members according to a long and rigorous process," the company said in an e-mailed statement. "As is the case with all BAPCo benchmarks, MobileMark 2007 was approved by BAPCo according to a democratic voting process similar to ones used by most industry work groups."