What the heck is the X8? Motorola's new processing system powers the Droid Ultra, Droid Mini and Droid Maxx, and it's anticipated to be under the hood of Motorola's new Moto X, coming tomorrow.

The X8 isn't a processor, and it isn't a system-on-a-chip. It appears to be shorthand for combining a customized Qualcomm Snapdragon S4 Pro SoC with two DSPs, one of which can function essentially as a low-power CPU.

"If you look at the X8 mobile computing system, it has a cluster of processors and then some separate elements of the system," said Iqbal Arshad, Motorola's senior vice president of engineering. The goal was to move away from a primarily CPU-based architecture to save power and do "intelligent, probabilistic computing," he said.

But still, let's start with the CPU; it's the easiest part to understand. The X8's CPU is, basically, a 28nm Qualcomm S4 Pro running at 1.7GHz. Motorola has customized the chip's firmware, though.

"We've done additional optimizations on top of that such as optimizing the entire Linux user space to move it to an ARM instruction set, cache optimization, Dalvik just-in-time optimization, and we've changed the file system," Arshad said. "It's full hardware-software integration to deliver best-in-class performance."

Here's where things get a little more mysterious. Associated with the S4 Pro, but not on the same chip, are a "contextual computing processor" and a "natural language processor." Arshad said that neither of those were ARM cores and declined to say where Motorola got them from, or who manufactured them.

"It's done by Motorola, a lot of design in the entire system," he said. "The actual silicon is specified by us but we don't go ahead and design and fab it. It's not an ARM processor, it's a very low-power separate processor," he said.

The contextual computing processor handles the sensors, display and touch interaction, but it also appears to function as the primary processor when the phone is in standby mode, including showing status and notification information on the display. The natural language processor deals with audio, noise estimation and noise cancellation; Motorola isn't using noise-cancellation technology from Audience or any outside vendor, Arshad said.

"We invented mobile. We have [80] years of DSP expertise, That is all Motorola's unique technology," he said.

Separating the custom logic from the CPU will allow Motorola to build X8s based on other CPUs, Arshad said.

"We can with with any Qualcomm processor. We can work with anybody's CPU. That's the beauty of it; all of our technology and experiences are decoupled from the legacy CPU processor," he said.

The combination of processors and custom firmware extends battery life and improves performance, Arshad said.

"If we did not have the contextual computing processor and our natural langauge processor in place, we would need two additional batteries," he said. The X8 also performs 50 percent better than "our competition" on gaming battery rundown benchmarks and can push higher graphics frame rates, he said.

Motorola also manages to do all of this without altering stock Android, he said. Here, I have to be precise: the version of Android on the Droids isn't exactly stock Android, but the Moto X is anticipated to be so.

"The Active Display system uses the exact same notification logic that's in stock Android, so we're not modifying that," he said.

The Moto X is launching in a series of events tomorrow; we'll be there.

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