41. MobileMark2005: System Performance And Battery Life

The MobileMark2005 test routines measure the behavior of a mobile computer running on its battery. For this comparison we used only two of this suite's battery life tests: Office Productivity and DVD Playback. Every test uses real-world applications and runs from the time at which the battery is fully charged and the power supply is disconnected from the test machine to the point when the battery is fully discharged and the PC shuts itself off.

Test results are written to a log file every 10 seconds. In addition, MobileMark 2005 constantly keeps tabs on two performance values during execution of the Office Productivity test: it calculates an overall performance value and an average response time for the completion of all activities that occur during this test. The overall performance value builds upon the average response time measured, but is expressed in relation to a standard reference system outfitted with average components whose value is set at 100 points.

Our analysis and conclusions follow the charts of test results.

Analysis Of Results

What looks like an error in measurement may be explained as follows: Whereas the Acer, Asus and HP notebooks match their CPU clock rates to application demands using SpeedStep or Dynamic Power Coordination, the Alienware Aurora M7700 uses AMD's PowerNow energy saving technology. To prevent the built-in desktop CPU from drawing maximum power and possibly damaging the battery sooner or later, the dual core FX-60 runs only at 1.2 GHz on battery power. In battery mode, the Alienware Aurora M7700 becomes the slowest machine in our test group and is surpassed even by the relatively pokey Acer Aspire 5672WLMi. This is not the end of the world. It's far more serious that the Aurora can't even play back a DVD flicker-free when running off battery power. Owing to a large number of dropped frames, Mobilemark2005's DVD Playback test didn't even report a score for the Alienware notebook!

As you can see from the values reported for the Office Productivity test, notebooks with Mobility Radeon X1600 chipsets can run for a long time from battery, if you play the game right. The "trick" that HP uses to make this possible is to throttle back the graphics processor and video clock rates to minimal values when running on battery power. Acer users the same trick as HP, and thus manages to attain acceptable system performance and reasonable battery life at the same time.

These rates remain set at maximal values on the Asus and Alienware notebooks, which explains why these notebooks suck their batteries dry quickly. In these notebooks we recommend lowering graphics processor and video memory clock rates manually, so as to achieve better battery lifetimes.