What's in a smartphone processor? Increasingly a lot

Whenever a hot new smartphone hits the market, one of the key specifications techies look at is its processor, which is primarily responsible for running the device's main computing functions and applications.

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But over the past few years, many processor chips have moved far beyond the traditional functions of plain old central processing units (CPU) and are now responsible for an array of functions including power saving, system memory and video processing.

"Computers used to have a CPU and then a bunch of other functions laid out on separate chips," explains Aaron Vronko, the cofounder of Rapid Repair. "Today they still have the same different parts but they're all packaged as part of same chip."

Take, for example, the newest iPhone processor, known as the Apple A4, which is built around an ARM Cortex-A8 core that takes up less than one-fourth of the entire chip. The rest of the processor is filled with power-saving logic cores, analog circuits and video digital-to-analog converters (DAC), among other features.

Kyle Wiens, the cofounder of iFixit, says that the chief advantage of putting so many functions onto one chip is that it allows handset makers to stack flash-memory chips directly on top of the processor chip, thus significantly speeding up the interactions between the core processor and the device's RAM. Additionally, he says that merging so many functions into one chip also significantly reduces processing time since it greatly lessens the physical distance of circuits within the device.

These sorts of design efficiencies are enabling the development of smartphone processors whose speed and power are increasing by leaps and bounds every year. Consider that last year's iPhone 3GS ran on an ARM Cortex A8 that clocked in at 600MHz; one year later, the Apple A4 processor is running at an even speedier 1GHz. Meanwhile, Qualcomm has already announced plans to release even faster processors, as it is slated to start shipping a 1.5GHz version of its Snapdragon processor series later this year that will be capable of supporting 1080p HD video applications on smartphones.

Room for improvement

Another upside to growing efficiencies in processor design is that it means the processor will also use power more efficiently than older CPUs. Saving power wherever possible is particularly important since most of today's smartphones have features that drain battery life at a much faster rate than processors ever could, especially 3G radios and LCD screens. This, notes Wiens is largely why today's smartphone processors have so many parts that are designed to shut off features that have been idle for a certain length of time.

"Over time we will see more and more circuits in these devices that are dedicated to saving power," he says. "They are going to be using lot more transistors to make sure that you're only using what you need to use at a given time."

The good news is that there's still a lot of room to improve processor efficiency, especially since there are still plenty of functions that have yet to be incorporated into the devices' main processor chips. In terms of the Apple A4, for instance, Vronko says that many of the peripheral functions, such as the GPS and cellular tower communication, are still separate from the central processor. Over time, Vronko expects chip makers will come up with even more ways to boost design efficiency and cram even more functions onto a single chip.

"The A4 is the first generation of Apple having its own processor," he says. "So I'd expect Apple to integrate more peripheral processors like GPS or the base band radio into the chip in future versions. That will translate to better manufacture design, better devices and lower manufacturing costs."

Wiens also expects chips to continue becoming more compact and complex, which will also add to the difficulty of ripping open smartphones and analyzing their guts.

"We can't just take apart the phones and look at what's inside them anymore," he says. "We have to take apart the chips themselves to see what's in them."

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