Ron Amadeo, writing for Ars Technica:
In addition to the usual Qualcomm Snapdragon 835 SoC, the Pixel 2 is equipped with the “Pixel Visual Core,” an extra, second SoC designed by Google with hardware-accelerated image processing in mind. At the heart of the chip is an eight-core Image Processing Unit (IPU) capable of more than three trillion operations per second. Using these IPU cores, Google says the company’s HDR+ image processing can run “5x faster and at less than 1/10th the energy” than it currently does on the main CPU.
The Pixel Visual Core is currently in the Pixel 2, but it doesn’t work yet. Google says it will be enabled with the launch of the Android 8.1 developer preview. At that time, the chip will let third-party apps use the Pixel 2’s HDR+ photo processing, allowing them to produce pictures that look just as good as the native camera app. The chip isn’t just for Google’s current camera algorithms, though. Google says the Pixel Visual Core is designed “to handle the most challenging imaging and machine learning applications” and that the company is “already preparing the next set of applications” designed for the hardware.
Having two entirely separate SoCs inside a smartphone is unusual. The Pixel Visual Core has its own CPU (a single Cortex A53 core to play traffic cop), its own DDR4 RAM, the eight IPU cores, and a PCIe line, presumably as a bus to the rest of the system. Ideally, you would have a single SoC that integrates the IPU right next to that other co-processor, the GPU. The Pixel 2 is based on the Snapdragon 835 SoC, though, and you aren’t allowed to integrate your own custom silicon with Qualcomm’s design. What Google can do is wrap a minimal SoC around its eight IPU cores and then connect that to the main system SoC. If Google ever set out to compete with Qualcomm’s Snapdragon line, an IPU is something it could build directly into its own designs. For now, though, it has this self-contained solution.
I’m willing to bet Google is planning to or already working on their own SoC. Once (and if) it goes to market, I wonder if they’ll be able to compete with Qualcomm and Apple, and how many years it will take them to catch up. Designing your own custom silicon is definitely a huge advantage, one which Apple is currently successfully leveraging over their competitors.