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Inside the iPad: Apple's new 'A4' chip

The first official Apple-branded chip, the fruit of Apple's acquisition of PA Semi, should have "a performance, battery efficiency, and cost advantage over the competition."

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.
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Brooke Crothers
3 min read

Along with the iPad, the Apple chip has arrived.

Called the A4, ("A" presumably for Apple), the most obvious difference with the chip in the iPhone 3GS is speed. The iPad's chip runs at 1GHz, compared to the estimated 600MHz (0.6GHz) of the iPhone 3GS. On Wednesday, at the event in San Francisco, the A4 was billed as "the most advanced chip" Apple has done yet. While fast, it's also frugal with power. "The A4 chip is so power efficient that it helps iPad get up to 10 hours of battery life," according to Apple's iPad Web page.

The Apple A4 system-on-a-chip
The Apple A4 system-on-a-chip Apple

By definition, the A4 is a system-on-a-chip, or SOC, that integrates the main processor, graphics silicon, and other functions like the memory controller on one piece of silicon--not unlike what Intel is trying to achieve with its future "Moorestown" Atom processor. And a similar SOC chip architecture is already used in the iPhone and other smartphones, such as Google's Nexus One and Motorola's Droid.

Based on what Apple has achieved with the iPhone 3GS, the chip should deliver a snappy interface. Of course, as in any 3G smartphone or laptop with a 3G connection, the 3G service can often be the weak link in performance, not the processor.

And speaking of 3G, the iPad will offer two AT&T plans. One is 250MB of data every month for $15; the other, an unlimited plan for $30 per month. Note that in the iPhone 3GS, Infineon supplies the 3G chip.

Apple CEO Steve Jobs described the iPad the "best (Web) browsing experience you've ever had. A whole Web page right in front of you that you can manipulate with your fingers. Way better than a laptop," in a video of the event streamed by CNET. That browsing experience, of course, will rely on the chip's ability to handle the background tasks as users access images and video.

Apple iPad packs Apple-branded chip in the half-inch-thin, 1.5-pound design.
Apple iPad packs Apple-branded chip in the half-inch-thin, 1.5-pound design. James Martin/CNET

But getting back to the A4, Ashok Kumar, an analyst Northeast Securities, says the system-on-a-chip is the fruit of Apple's internal development though its core processor is still based on a design from United Kingdom-based ARM. In Apple's own words, it's "custom silicon that we designed for this product." Apple acquired chip designer PA Semi in 2008. And it is worth pointing out that this is the first time Apple has announced an Apple-branded chip.

Richard Doherty, director of technology consulting firm Envisioneering Group, in an interview last week said this about the Apple chip technology versus competing silicon from companies like Qualcomm, Freescale, and others that license the basic design from ARM: "There's nothing that I can see from ARM licensees or Intel that could challenge the power-per-watt, the power-per-buck, the power-per-cubic-millimeter of size. Apple is going to have quite a performance, battery efficiency, and cost advantage over the competition."

Another technology worth noting is the screen. The display uses IPS, or in-plane-switching LCD technology, which delivers quick response times for viewing video and wide viewing angles. Well-executed IPS designs show little color or brightness change when viewed from the side.

Updated on January 28 at 10:45 a.m. PST: adding discussion about A4 chip and its ARM origins.