But it's also designed to meet requirements for a very wide range of end products, from smartphones to big servers. Apple will forgo ARM's A15 designs but create an A15-class CPU of its own specifically for mobile devices. "Having control of the CPU allows Apple to optimize the design to meet its own needs," Linley says. "Apple is willing to spend a little more money -- on a more expensive CPU -- if it makes the end product, such as an iPhone, noticeably better."
According to a battery of initial tests by Anandtech.com, Apple has done exactly that with its first custom CPU, running the iPhone 5.
"Overall, the performance of the A6 CPU cores seems to be very good," writes Anand Lal Shimpi. "Apple claimed a 2x CPU performance advantage compared to the iPhone 4S during the launch event for the 5. How does that claim match up with our numbers? Pretty good actually. ... This is hardly the most comprehensive list of CPU benchmarks, but on average we're seeing the iPhone 5 deliver 2.13 times the scores of the iPhone 4S."
Part of the gain is realized by moving to a smaller die process for the chip, to 32 nanometers from 45 nm. But by itself that's not enough, according to Lal Shimpi.
Among his findings:
+ "The memory interface on the A6 seems tangibly better than any previous ARM based design, and the advantage here even outpaces Intel's own Medfield SoC."
+ "The A6 ... features a three core PowerVR SGX 543MP3 [graphics processor], running at higher clock speeds to deliver a good balance of die size while still delivering on Apple's 2x GPU performance claim."
+ "The result is compute performance that's similar to the A5X in Apple's 3rd generation iPad, but with a smaller overall die area."
+ "As we've seen in the past, these gains don't typically translate into dramatically higher frame rates in games, but games with better visual quality instead."
The iPhone 5 ranks at or near the top in these benchmarks, compared with an array of high-end rivals. Lal Shimpi noted that Qualcomm's ARM-based Snapdragon S4 Pro CPU with Adreno 320 GPU puts LG's Optimus G "hot on the heels of the new iPhone."
Why not just run the Cortex-A9 cores found in the earlier Apple A5 SoC at a higher frequency?