Apple's New A7 Chip Goes Under the Microscope

Apple's iPhone 5s is powered by the brand-new A7 mobile chip, which features the ARMv8 architecture—making it the first processor attached to a mainstream consumer product using ARM's 64-bit instruction set.

What benefit that affords buyers of the new iPhone isn't totally clear. Apple's move from 32-bit chips to 64-bit, which increases the amount of virtual memory the processor can use, doesn't seem likely to impact the development of software for iPhones in the near future. In the iPhone 5s, the A7's dual-core, 1.3GHz CPU taps into only about a quarter of the 4GB of RAM that represents the maximum amount that can be referenced, not by a 64-bit central processor, but by a 32-bit CPU.

So why make the move to 64-bit? PCMag's Sascha Segan and other mobile analysts think the decision was a hedge on the future, when Apple may want to tie together iOS, the software platform for iPhones and iPads, with its Mac operating system, which has supported 64-bit computing for a decade.

Whatever Apple's reasons behind transitioning to 64-bit, the A7 offers a hefty performance bump over its predecessor, the iPhone 5's A6 System-on-a-chip (SoC), as our mobile team discovered after benchmarking the new chip for overall system performance, Web browsing, and graphics performance.

In fact, the A7 doubled the performance of the A6 in several key benchmark tests we ran (though as mobile analyst Eugene Kim sagely noted, synthetic benchmarking should always "be taken with a grain of salt"). In addition to the redesigned CPU, the A7 also includes a PowerVR G6430 GPU, according to AnandTech.

So how did Apple accomplish such a generation-over-generation performance bump? Here we turn to the folks at iFixit, who recently called upon its friends at Chipworks to pry open the A7's package and peel away semiconductor layers with its ion beam etcher before training an electron microscope on the more than 1 billion transistors populating the SoC.

Measuring the distance between transistors on the A7 shows denser circuitry.

Apple moved to the 28-nanometer node for the A7 —the Samsung foundry's 28nm, high-k metal gate (HKMG) process, to be specific. This was publicly known but confirmed by Chipworks during their investigation, which involved measuring the size of the A7's transistors and the distance between them (pictured, right). Going to 28nm means that with the A7, Apple can squeeze the same amount of transistors on about 77 percent of the area used by the 32nm A6 to cram in that much circuitry, the chip teardown experts noted.

What's more, the A7 is actually a bigger chip than the A6. More densely packed transistors over more total surface area than the last-generation SoC equals a significantly more powerful compute engine.

The A7 also benefits from Apple's inclusion of a new chip, the M7, in the iPhone 5s. The M7 (pictured, below) is a motion coprocessor that handles the collection and processing of sensor data generated by the smartphone, tasks formerly handled by the device's main A-Series SoC. Offloading these processes to a separate chip obviously gives the A7 more resources to devote to CPUing and GPUing, but it's also a battery life extender, according to Apple.

A closer look at the new M7 motion coprocessor in the iPhone 5s.

And now we have an identity for the M7, courtesy of Chipworks, which reported that it is "an NXP LPC18A1, part of the LPC1800 series of high-performing ARM Cortex-M3 based microcontrollers."

As iFixit noted, this is the same basic part used for motion tracking in the Oculus Rift virtual reality gaming headset.

"The M7 is a new direction for Apple. In an effort to reduce power consumption, the M7 chip is dedicated to collecting and processing accelerometer, gyroscope and compass data," Chipworks said.

The iFixit gang also asked Chipworks to help identify the makers of those specific sensors in the iPhone 5s and here they are:

• Bosch Sensortech BMA220 3-axis accelerometer
• STMicroelectronics 3-axis gyroscope
• AKM AK8963 3-axis magnetometer

The teardown sites also zoomed in for a closer look at the iPhone 5s's new iSight camera, which maintains the 8-megapixel resolution of the iPhone 5's camera but has a 15 percent larger active pixel array area. The Wi-Fi module, Broadcom's BCM4334, is the same one found in the iPhone 5.

As anticipated, the new iPhone sports Qualcomm's MDM9615M 4G LTE modem, which all the cool new smartphones are using. As for the rest of the RF capabilities, iFixit and Chipworks identifies the following responsible ICs:

• Skyworks SKY77810 2G/EDGE Power Amplifier
• Avago A792503 Band 25/3 Power Amplifier
• RF Micro RF3763 Band 5/8 Dual Power Amplifier
• Skyworks SKY77572 Band 18/19/20 Power Amplifier
• Skyworks SKY77496 Band 13/17 Power Amplifier
• TriQuint TQF6414 Band 1/4 Dual Power Amplifier

For more, check out PCMag's full reviews of the iPhone 5s and iPhone 5c, as well as our review of iOS 7.