Over the last week, more and more details of Apple's custom A6 processor design have come to light, including a custom armv7s-compatible core design and its triple-core GPU. Detailed analysis by Chipworks and iFixit have revealed that Apple's custom ARM core design appears to have been laid out by hand instead of by computer algorithms—a time-consuming process that can result in optimized high-frequency operation.

Engineers at Chipworks used ion beam etching to remove all the casing material from the A6's die, and then used a variety of high-powered microscopes to peer into its structure. The detailed layout of the dual ARM cores isn't typical of integrated circuits that are increasingly laid out using software, instead suggesting an approach that is becoming more rare in today's microprocessors.

"It looks like the ARM core blocks were laid out manually—as in, by hand," iFixit's Miroslav Djuric said via e-mail. "A manual layout will usually result in faster processing speeds, but it is much more expensive and time-consuming."

"The manual layout of the ARM processors lends much credence to the rumor that Apple designed a custom processor of the same caliber as the all-new Cortex A15," according to Djuric, referring to its compatibility with the more advanced armv7s architecture also used by the Cortex A15. The previous A5 design used a tweaked Cortex A9 core, which is less powerful at the same clock speed than either the A6 or the Cortex A15 and uses the less-capable armv7 architecture.

That time-consuming manual layout process would also certainly help explain why it took Apple over four years from its acquisition of fab-less design firm PA Semi to release its own custom silicon for its mobile devices. Based on our experience with the iPhone 5, the hard work is paying off in spades.

The overall A6 die area is 96.71mm2, compared to approximately 70mm2 for the 32nm variant of the A5 processor. A close look at a cross-section of the A6 confirms that it is also built on Samsung's 32nm high-K process, giving Apple extra area for additional functional blocks, like the dedicated image signal processor and extra GPU core.

iFixit and Chipworks also peeked into a few other chips on the iPhone 5's logic board, including an Apple-branded digital audio amplifier from Cirrus Logic, a Murata Wi-Fi module, and Qualcomm's MDM9615 baseband.