I also ran our standard encoding tasks, where we take a 30GB MKV file and transcode it using HandBrake to a size and format friendly to an Android tablet. It's a heavy workload for a laptop, but not unheard of considering the capability of laptops.
While you don't need a big CPU in office tasks, you can see where the dual-core Core i5 chips, with their greater power consumption and higher clock speeds, have an advantage. With a third of the thermals to work with, the dual-core Core M 5Y10 just doesn't have the megahertz to keep up with the pack, but it's still respectable. I wouldn't let this be a deal-breaker unless CPU-intensive chores are Job no. 1. If so, it's worth paying for a Core i7 part instead, but in general, most people won't notice much of a difference with a Core M.
Core M lacks in graphics power, too
The Core M CPU is about low power and low thermals. What you get is better than Atom/Celeron/Pentium performance, but still far less than a full-tilt Core i5 chip using a CPU that consumes three times its power. That becomes very apparent in our HandBrake encoding test, and also running the graphics test 3DMark Cloud Gate. As you can see, you give up a lot of performance. Granted, the integrated graphics in an i5 won't let you play a graphically intense game at any reasonable frame rate, but the Core M's gaming chops take a definite backseat — they're about the equivalent of HD4000 graphics in an older Ivy Bridge CPU.
Decent battery life
Perhaps one of the most important metrics in a laptop is battery life. I ran MobileMark 2014 on the ZenBook and then compared its numbers to the Lenovo ThinkPad X1 Carbon and both Dell XPS 13 units.
MobileMark 2014 is a real-world rundown test, using off-the-shelf popular apps such as Office and Photoshop and replicating a typical work session. The test simulates a person pulling up an email and sitting there and actually reading the email for five minutes, for instance, rather than simulating a person typing like an automaton for eight hours straight.
With its 45-watt-hour battery and power-sipping Core M chip, the Zenbook lasted a healthy 638 minutes. The Dell XPS 13 2015, with its even larger 52-watt-hour cell (but higher-res screen) comes in a bit worse, at 602 minutes. I also had time to test the most natural competitor here: Dell's XPS 13 2015 with 4GB of RAM, a 128GB SSD and 1920x1080 screen. With a sticker price of $799, it's the most direct competitor to the ZenBook. You can see what happens to the Dell XPS 13 once you shed the high-resolution panel and touch option: A healthy bump from 602 minutes to 728 minutes.
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