In unveiling the iPhone 5s this week, Apple executives proudly pointed to several hardware firsts. Among the most obvious are the new Touch ID fingerprint sensor in the home button and the move to the 64-bit Apple-designed A7 processor. (Samsung was quick to announce that it's developing devices with 64-bit chips, too.) Along with those under-the-hood advances comes the most intriguing change: the new M7 "motion coprocessor."
Apple hasn't publicly detailed just how the the M7 works, though it has added a new set of APIs, dubbed CoreMotion, that developers can access when writing iOS 7 apps. Nike, in fact, has already announced the first M7-enabled app.
Apple did at least offer a broad overview of its intentions for the coprocessor: "Every iPhone 5s includes the new M7 motion coprocessor that gathers data from the accelerometer, gyroscope and compass to offload work from the A7 for improved power efficiency." That's from Apple's press release announcing the 5s, and it mirrors what Phil Schiller, Apple's senior vice president of worldwide marketing, said on stage during the iPhone announcement Tuesday.
This defines a huge function of the M7 -- to process the increasingly large amounts of data people can generate while carrying a sensor-laden device. Triangulating this data takes processing power, but not a huge amount of it. (Remember, earlier iOS devices, including those that used less powerful non-Apple processors, were able to work with this kind of data.) Essentially, the A7 would be overkill for the more basic tasks of aggregating and processing motion data.
Offloading that low-level data capture and processing to a low-power processor delivers two big advantages: It increases battery life (always an important goal for any mobile device), and it reduces the heat generated by the main processor. That should increase the life expectancy of a device and keep it from getting hot. As processors grow in capacity and performance, they typically need more power to function (and therefore, typically, produce more heat). One explanation for the M7 is simply that Apple needed to offset some of the increases in power demand and heat production that are a consequence of the A7 chip's improved performance.
The second big advantage of the M7 is that it effectively boosts the performance of the main A7 processor. With less work to handle during iPhone use, the A7 has more processing cycles available for other needs like launching and running apps. With iOS 7 being better at multitasking, this gives the iPhone 5s additional performance dividends.
Apple is also touting the M7 for tasks that take place when you're not actually using your iPhone. Since it uses less power than the A7 processor (and potentially less power than earlier A-series processors), iOS 7 and apps coded to take advantage of it can perform continuous monitoring in a way that might otherwise be impossible or unwieldy because of power constraints.
Apple is specifically pitching this as an advantage for fitness and activity-tracking apps, saying that, thanks to the M7, the iPhone 5s "continuously measures your motion data, even when the device is asleep, and saves battery life for pedometer or other fitness apps that use the accelerometer all day."