Absolute Power


A breath of fresh Air

This blog originally posted on the Low Power Engineering Community 12/2/10. 

This month, a little diversion from our recent deep dive into smart phones – I recently received in the mail my new MacBook Air!  First of all, kudos to the order fulfillment process.  I ordered my new baby on Friday.  It shipped from Shanghai on Saturday, and arrived at my door on Monday.  No special or delivery charges needed.  I had to order online in order to max out the memory, both RAM  (4GB) and SSD (128GB), as well as the processor (1.6GHz).  And it was worth the wait – this little (11.6’) machine runs really well considering its processor is somewhat dated, and it LOOKS GREAT!  At 2.2 pounds (most of which is batteries) and sporting a 16:9 screen, it’s a natural for video, surfing the web, or any other activities you’d normally do on your laptop.  Microsoft Office (2008) runs nicely, as does Adobe CS5, and VMWARE Fusion 3.  I even spent quite a bit of time running StarCraft II over Thanksgiving (as a gaming benchmark only, of course), and it did a reasonable job as long as the graphics settings were medium to low.

So it’s a wrap, right?  Not so fast…!  We all know from our recent investigations that we’ve gotten beyond just the specs on computers these days – GHz and GB are no longer the most meaningful metrics.  And while running real world applications can tell us something about the utility of computing devices, for portable electronics, it’s all about battery life, or power efficiency.  So I ran the Air through my recent power testing setup – determine the power efficiency of the machine for playing back our reference movie, “Star Trek”!

The current champion for personal movie watching has to be the iPad – it’s a great combination of function and form, with a beautiful display and fantastic battery life.  Watching “Star Trek” on these two machines was a great experience – both are very compelling as portable video players.  The Air has the definite advantage in screen size – it’s 16:9 aspect ratio was a better fit for the movie, resulting in a significantly larger picture even though the displays physically aren’t that much different in size (11.6” vs. 9.7”).  Both displays were nice and bright, but the iPad definitely wins for picture crispness and clarity.  The Air’s display is nice, but just did not seem to have the extra depth and contrast of the iPad display.

In terms of power efficiency, the Air carries a lot of baggage (for just watching a movie) – MacOS and the laptop platform is much more complicated than iOS, so we’d expect to see that overhead in the numbers.  And we sure do!  The iPad dissipated 6.2 Wh of energy to view Star Trek on maximum brightness and sound.  On the MacBook Air, the same setup used over 21 Wh of energy, nearly 3.5x!  Removing the display from the equation doesn’t help – with brightness and sound at minimum, the iPad uses 3.2 Wh of energy, compared to the Air’s 14.0 Wh.  That’s a 4.5x difference in energy efficiency.

So where does the new MacBook Air fit in today’s lineup of portable computing devices, and does it threaten the exploding market for the iPad and other tablets?  In my mind, it carves out a nice niche in the “ultraportable laptop” category, sitting between tablets, netbooks, and more traditional laptops.  With good performance, reasonable battery life, and style to spare, this category may well indicate the future of our laptops, absorbing the netbook category, as well as low-end traditional laptops.  But watch out for the growth of tablets in coming years.  Today’s tablets are attacking mobile computing from the standpoint of smart phones as opposed to laptops, and that philosophy seems to bring ultra-high efficiency, novel features, and slick packaging.  The Microsoft Office app can’t be far behind.

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