iPad 3: L.H.O.O.Q., by Ken Werner

In 1919, the French artist Marcel Duchamp took a cheap postcard reproduction of the Mona Lisa, and added a beard, moustache, and the letters “L.H.O.O.Q.”  When pronounced in French, the letters sound like the sentence “Elle a chaud au cul,” which can be translated as “She has a hot ass.” My old art history teacher (well, he would be old now) had a less delicate interpretation, which made it clear that “L.H.O.O.Q.” was Duchamp’s attempt to explain why the Mona Lisa is smiling.

Now, thanks to Consumer Reports and comments from some of the 3 million people who bought Apple iPad 3s  in its first 5 days on the market, we know that L.H.O.O.Q. applies to the new iPad, as well.

Consumer Reports used a thermal imaging cameral to determine that portions of the back of the new iPad reached 113 degrees Fahrenheit unplugged with WiFi on but 4G off. That’s about 13 degrees hotter than an iPad 2 used for comparison. When the new iPad was run plugged in, playing Infinity Blade II steadily for 45 minutes, the temperature reached 116 degrees F. What would the temperature have been with the notoriously power-hungry 4G turned on?

In general, the hotter temperature shouldn’t come as too much of a surprise. The new iPad has a 42.5 watt-hour battery compared to 25 watt-hours for the iPad2. Since the operating time per charge remains unchanged at 10 hours, according to Apple, it is clear that the new iPad uses an average of 70% more energy per unit time than the iPad 2, and the associated heat has to go somewhere.

The additional energy consumption has been attributed to the 4G LTE radio, the new dual core A5X processor with quad-core graphics, and the 9.7-inch, 2048×1536 “Retina” display. What hasn’t been discussed is how much of that energy consumption can be attributed to the late design change from a display with a metallic oxide semiconductor backplane to one made from good old amorphous silicon (a-Si). As mentioned previously in Display Daily, Sharp was unable to supply the oxide-driven displays when Apple and Sharp had anticipated, with the result that Apple turned to Samsung and LG for displays using a-Si. The a-Si thin-film-transistors (TFTs) must be considerably bigger than the oxide TFTs were planned to be, thus producing a smaller aperture ratio and requiring more backlight output (and battery use) for any give display luminance. It is easy to speculate that the overall system design was done with the oxide TFTs in mind. Would the battery life be longer than ten hours if it had been possible to use the oxide-TFT displays? Or would the battery have had less capacity and been lighter and less expensive?

You can think about these questions the next time you watch Mission Impossible or play Infinity Blade II, and are reminded once again that your new iPad has a hot ass.

Ken Werner is Principal of Nutmeg Consultants, specializing in the display industry and display technology.  You can reach him at kwerner@nutmegconsultants.com.