Gateway E-155-C: A Lightweight Convertible

Battery Life

In the past, our standard battery life test has been provided courtesy of MobileMark 2005. Since we're now moving towards testing with Windows Vista (which MobileMark 2005 doesn't support), we needed to come up with a new method to determine battery life. Generally speaking, we don't expect people to seriously tax their laptops when they are unplugged, so we tried to create benchmarks that will simulate normal use.

For the first battery test, we use Internet Explorer to simulate surfing the web. We have a script that starts Internet Explorer and loads our three homepages, all of which contain quite a few Flash-based advertisements. The script then sleeps for 60 seconds, simulating "reading" a web page(s), after which Internet Explorer is shut down and reloaded. Internet Explorer is set to delete all temp files on exit, in order to continue to generate hard drive activity. The other battery life test is simply DVD playback, and we use Star Wars Return of the Jedi as our test DVD. Basically, the Internet Explorer test corresponds to about the best case scenario you are likely to encounter, while the DVD test is a bit more taxing.

Gateway sent us both their 4-cell and 6-cell batteries for testing. The results are summarized in the following table, along with scores for the HP dv6500t.

Battery Life (Minutes)
	HP dv6500t 6-cell	HP dv6500t 12-cell	Gateway E-155-C 4-cell	Gateway E-155-C 6-cell
Internet Explorer (Max. brightness)	133	246	111	168
DVD Playback (Max. brightness)	105	205	98	146

The default 4-cell battery doesn't provide a lot of battery life unless you turn down the display brightness. Since we felt the display was already relatively dim, we certainly wouldn't want to use the laptop at reduced brightness settings. However, for the record we were able to improve battery life by 30 to 35% by running the display at minimum brightness. Moving to the 6-cell battery increases battery life by about 50%, as expected. In the near future, Gateway will also begin shipping 8-cell batteries - they are already selectable in the online configurator.

Another anomaly that cropped up concerns brightness, so we'll address that now. Windows Vista would periodically adjust the display brightness while we were using the system, for no apparent reason (though not during our battery benchmarks, thankfully - it appears to be related to input from the keyboard/mouse). Sometimes the LCD would get darker, and sometimes it would get lighter. The E-155-C has three keys that allow you to adjust the display brightness. Two of these are used to increase or decrease brightness, while the third appears to cycle between three settings (minimum, medium, and maximum). Unfortunately, for some reason Windows Vista disables the increase/decrease brightness keys. (We experienced the same problem with the HP dv6500t.) We would assume this is another driver issue, though whether it's the display drivers or something else we can't say.

Power Consumption

Related to the battery life discussions we've just finished, we have power results. For power testing, we remove the battery from the laptops and measure system power draw at the wall outlet using a Kill-A-Watt device. We test several different scenarios to try to isolate the power draw of the various components. First, we have the baseline measurement when the system is idle and sitting at the desktop. No applications are running for 10 minutes or more but the screensaver and hard drive sleep mode are disabled. As a CPU load test, we run the SMP version of Folding@Home at 100%. Finally, for maximum power load we leave Folding@Home running and start 3DMark05. In this way, we can see roughly how much power the GPU is using in 3D mode versus 2D mode.

System Power Draw (Watts)
	ABS Mayhem Z5	ASUS A8JS	ASUS G2P	Gateway E-155-C	HP dv6500t
Idle	44-49	26-32	43-52	16-21	22
100% CPU	67-71	47-52	71-81	25-30	57
Maximum	100	71	97	34	67

The E-155-C doesn't consume a lot of power, and clearly a large portion of the power is going to the display. The difference between maximum and minimum brightness is about 5W, so maximum brightness increases idle power consumption by over 30%. The maximum power draw of the system when the CPU is under full load increases by 9W, so the display still increases total system power draw by 20% under load. Given the relatively small battery capacity, every additional watt of power draw can have a noticeable impact on battery life. We're looking forward to testing some laptops that use LED backlighting to reduce the LCD power requirements without compromising on brightness levels.