Apple 's special iTunes event was notionally about the snazzy new iPods and Apple TV, but it also reveals how much the company's future hinges on its house-brand ARM chips--the A4 silicon is now inside four keystone Apple gizmos.
When the iPad  arrived, one of Apple's selling points was that it includes a custom processor--"custom silicon" as it was called. Apple's chip actually wasn't strictly its own, since it used licensed ARM architecture and is fabbed by Samsung , but the customization of the design is definitely a Cupertino affair. By having control over the design right down to chip level, Apple promises to deliver a vertically integrated product that is both good at raw computing power and consuming small amounts of energy from a device's battery.
When the iPhone 4 arrived this year, it wasn't much of a surprise to see the A4 in there: It has all of the same design requirements as for the iPad, and the computational power the A4 squeezes into the already-slick iPhone makes the device's performance a notable stand-out in the market. Using the same component also represents all sorts of economies of scale for Apple. It simplifies hardware-level coding matters, and the job of app writers, and Apple may even be able to negotiate on the unit price of the chips from the foundry as it'll be ordering so very many of them.
With yesterday's event, Apple launched a refreshed iPod Touch--containing, of course, the A4 chip. Everyone expected it, but Apple made sure to mention the fact. Then came the surprising "one more thing" announcement of the refreshed Apple TV , a tiny set-top box that runs a custom operating system (which has us wondering if iOS is hidden in there, somewhere, ready for a future update to bring the App Store to your TV) on top of low-power-consuming hardware... with an Apple A4 chip at the core.
With the exception of the iPod Nano, Shuffle and Classic all of Apple's small devices now run on the same processor. Apple's trumpeted it, aggressively patented  it, and, apart from the manufacturing chain, is now no longer at the whim of another big company--and potential competitor--as it determines the upgrade path of its processors.
The Mac desktop line still relies on Intel's CPUs, of course. Apple took a huge step and switched from IBM Power PC architecture in 2006 after a 14-year run, so it's unlikely to change that very soon. But it seems inevitable that at some point, Apple will update its desktops using more powerful ARM-based designs--like the newly revealed Cortex A9 multi-core reference architecture--which could bring all sorts of benefits to Apple's cleverly multicore-centric OS X operating system.
Just as Apple has adopted an external style that extends across its entire product range, its silicon is now part of the company's design thinking as well. By the time the A5 (or A8?) chip arrives in 2011, it will be even more important to Steve's company.
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