In the cellphone world, a chip is a chip. Most of them are ARM-based but there are a few outliers. Most importantly, however, each has a similar power profile. Therefore, by controlling the entire chip themselves, Apple can handle its own graphics, video, and audio output as well optimize for power control – a huge concern with devices like the iPhone.
Quoth the WSJ:
In one sign of the new focus, Apple recently hired Raja Koduri, who was formerly the chief technology officer of the graphics products group at chip maker Advanced Micro Devices Inc. Mr. Koduri started at Apple this week, following in the footsteps of Bob Drebin, who had held the same title at AMD and is also now working for Apple. Online job postings from Apple describe dozens of chip-related positions it is trying to fill, some with partial descriptions like “testing the functional correctness of Apple developed silicon.”
This is Apple’s MO: build an all-star team in stealth mode and launch their internal product to much rejoicing. As expected, Apple declined to comment.