So here's what's in the schematic in the article:
TLDR: This is a barometric pressure sensor, and most definitely not a processor of any type. I think it's safe to assume that we can expect a pressure sensor in the next iPhone- many other phones have found uses for them.
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The first thing that threw me off- if this was the M7 or some kind of other 'processor', it would tend to communicate with sensors in a master-slave fashion over a serial protocol like SPI or I2C. It would also need some kind of data link back to the A7 (or A8 or whatever), most likely another serial line. That's not present in this diagram.
The stuff on this schematic is labelled like SPI, or a similar protocol. The line coming in from the top left is labeled MOSI- this stands for master out, slave in- it's a serial data line (going one way). It's connected to the SDI pin of the chip (serial data in), meaning that this chip must be a slave to the master SPI controller, and not the M7 or successor.
It is common to have multiple 'slave' chips hooked up to the same master (sharing data lines, one MISO and one MOSI). The master selects which chip it wants to talk to with a CS line (chip select). This is the line at the bottom left, the only one with 'PHOSPHORUS' in the net name. Since that CS line would be selecting PHOSPHORUS, and PHOSPHORUS is a slave, that tells me that PHOSPHORUS must be whatever this chip, probably a sensor (see more below!).
OSCAR was the code name of the M7, and the serial lines are labelled such that they go from sensors (e.g. the IMU) to the M7. I'm not making much of the fact that the serial lines going to this chip have labels saying they go from OSCAR (the M7) to the IMU, but are actually connected to this chip- I think they are probably just shared serial lines.
The chip pictured has the part number BMP282. I'm 99.99% sure this is a Bosch barometric pressure sensor, similar to this part
BMP280 . Variants of one part often have slightly different part numbers- if Apple got Bosch to customize the chip for them with different packaging, or a slightly different measurement range, that would explain the difference in part number.
EDIT:
Here's what Bosch says the BMP280 chip is commonly used for:
* Enhancement of GPS navigation (e.g. time-tofirst-fix improvement, dead-reckoning, slope detection)
* Indoor navigation (floor detection, elevator detection)
* Outdoor navigation, leisure and sports applications
* Weather forecast
* Health care applications (e.g. spirometry)
* Vertical velocity indication (e.g. rise/sink speed)
Spirometry is measuring breath/lung function.