MacBook Air: New design meets old chip

The new MacBook Air is an ultrathin wonder, packing the performance of lower-end mainstream laptops into a sub 3-pound design. There's a catch, however.

Brooke Crothers Former CNET contributor
Brooke Crothers writes about mobile computer systems, including laptops, tablets, smartphones: how they define the computing experience and the hardware that makes them tick. He has served as an editor at large at CNET News and a contributing reporter to The New York Times' Bits and Technology sections. His interest in things small began when living in Tokyo in a very small apartment for a very long time.
Brooke Crothers
4 min read

The new MacBook Air offers an interesting paradox: a spanking-new, ultra-thin design that is wrapped around old Intel chips.

The just-announced 11.6-inch and 13.3-inch Airs are a marvel of thin design, with the smaller model weighing in at only 2.3 pounds and both models only 0.68 inches at the thickest point. What Apple CEO Steve Jobs described as MacBook-meets-iPad. And inside is Apple's latest and greatest flash storage technology that sits directly on the system board as well as a new higher-performance Nvidia GeForce 320M graphics chipset.

Also inside are old Intel processors. How old? Old enough to date back to the same line of processors used in the original MacBook Air, announced three years ago come January. No power-efficient--and much newer--Intel Core i3, i5, or i7 processors here. So, what gives?

Here's the pithy, tepid statement that Jobs made Tuesday during the MacBook Air rollout: "The Core 2 Duo is a fast processor for this class of machine." And Apple had this to say in its press release yesterday. "Flash storage combined with power-efficient Intel Core 2 Duo processors and Nvidia GeForce 320M graphics delivers an ideal balance of mobility, battery life and performance."

But digging a little deeper, the reason is really no different than the rationale given for the 13-inch MacBook Pro, which also uses Core 2 Duo processors. In short, real estate. Because Apple needs to tap into the performance goodness of the graphics processing units (GPUs) from Nvidia--even in a highly compact design like the MacBook Air--Apple can't use a new Core i series processor because it would require too many chips: an Intel Core i5 processor (as an example), an Intel chipset, and the discrete Nvidia GPU. (Also: see Additional Notes at bottom.)

New 11.6-inch MacBook Air logic board: the Intel Core 2 Duo processor (red) and the Nvidia graphics-centric chipset (orange).  This two-chip solution allows Apple to tap into more powerful Nvidia graphics. 2GB RAM module is below (yellow).
New 11.6-inch MacBook Air logic board: the Intel Core 2 Duo processor (red) and the Nvidia graphics-centric chipset (orange). This two-chip solution allows Apple to tap into more powerful Nvidia graphics. 2GB RAM module is below (yellow). iFixit

Apple solves the real estate problem by using a two-chip design (see graphic): the Core 2 Duo and the Nvidia GeForce 320M chipset. And the Nvidia chipset includes the functions that would otherwise be present in an Intel chipset. What some observers miss is that the Nvidia 320M is a chipset, not a discrete GPU. And it follows that because real estate is not as big a concern in the larger MacBooks (15- and 17-inch) Apple can use the Intel Core i5 processor, an Intel chipset, and a discrete Nvidia GeForce GT 330M GPU--which Apple does.

And digging even a little deeper, there are other reasons. "Apple for the last two years has tried to include in all of its systems GPUs that have some capability to be used for programmable operations that take advantage of OpenCL. Apple has been driving this OpenCL standard--which Intel does not support in its integrated graphics offerings," according to Nathan Brookwood, the principal analyst at Insight 64.

Brookwood continues. "Apple is using the GPU to speed up some of the more computationally intensive tasks like face-tagging in iMovie and iPhoto. Those are the kind of tasks that really lend themselves to GPU acceleration," he said.

So, we're left with a good, but not great, Intel Core 2 processors and a "powerful"--as Apple puts it--Nvidia GeForce 320M chipset.

Additional Notes:
Another reason that Apple opted not to go with the UM series of Core i3, Core i5, or Core i7 power-efficient processors--what Intel generically calls ultra-low voltage processors--may be related to the total power envelope, also referred to as the Thermal Design Power or TDP. (This discussion gets a little complicated and hair-splitting so don't read on unless this is something of real interest to you.)

Core i Series vs. Core 2 Duo--Thermal Design Power:

  • Core 2 Duo SU series (used in the 11.6-inch MacBook Air): 10 watts (W)
  • Core 2 Duo SU series associated chipset, the GS45: 8W. (So, a total of 18W with processor).
  • The Core i UM series: 18W
  • The Core i UM series associated chipset, the HM55: 5W. (So, a total of 23W with processor.)

The Core i5 CPU has a larger TDP because it integrates more functions--such as graphics, which used to be in the chipset--than the Core 2 Duo. But that is a moot point for Apple because it has decided not to use Intel's graphics. Nvidia does not publish the TDP on the 320M chipset. But, remember, it is not possible to use an Nvidia chipset with Intel Core i series processors so Apple would be forced to use a discrete Nvidia GPU and that would entail an Intel chipset (making for a total of three chips), ultimately jacking up the TDP over what the Air can handle.

Updated on October 22 at 3:10 p.m. PDT: adding notes at bottom.

Updated on October 23 at 11:25 a.m. PDT: modifying "moot point" discussion.