

IPhone M7 chip counts your steps even after the battery dies - umsm
http://www.iphonehacks.com/2014/03/iphone-5s-m7-chip-battery.html

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supercoder
When the M7 chip was first announced, there was much speculation as to why it
was a separate chip rather than part of the main CPU.

A fair number of people were reasoning it could suggest it would be used in
some other unannounced device (such as a watch etc).

While that's still possible of course, this is a much simpler explanation for
the decision to have it as a standalone chip.

