When the great folks at iFixit did a teardown of the iPhone 4 back in the summer of last year they came across a mystery chip that they couldn't ID. Well, now that mystery has been solved.
Here's the chip on the mainboard of the GMS iPhone 4:
And here's the same chip in the CDMA-variant of the iPhone 4:
So what is it? Well, iFixit could take the suspense no more and got Chipworks to decap the chip and discovered a name:
So what is it? It is a low-power digital audio signal processor used by the iPhone for noise-cancelling.
Here's a video of the noise-cancelling technology, which iFixit say outperforms every non-Audience powered cell phone, in action: