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Can cognitive layering meet challenges of power design?

03 Oct 2014  | Nick Flaherty

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Editor's Note: Chris Rower, founder of configurable processor IP company Tensilica, developed the term "cognitive layering" for power design. Continue reading to know more about it.

An explosion of design options is happening with system-on-chip (SoC) devices for the Internet of Things, driven largely by the power demands. We're on the cusp of new products that use less power, says one engineer, Chris Rowen. He should know. As founder of configurable processor intellectual property (IP) company Tensilica and now heading up the IP business of Cadence Design Systems, Rowen thinks about power a lot and has done serious time making circuits run more efficiently.

Chris Rowen

Chris Rowen

"System architects are responding to the demands of the flow of power and how we fit all the parts together, and you will see products coming out in the next few months that reflect this strategy," he told EE Times.

64bits of data is especially hungry for energy. "There is a huge range in the energy to move 64bits of data. At the lowest scale there's one transistor, at the other end of the spectrum is the cost in energy for 64bits of dialogue with a server farm," Rowen said. "In between, there's disc access, register files, applications processors and what you find is a scale of over 12 orders of magnitude in energy usage."

Because of this, it's natural to push as much processing as local as possible and only go to the cloud when absolutely necessary, he says, and as a result chip architects are thinking much more carefully about locations of access and it has a profound effect on what is happening in IoT.

He coins the term "cognitive layering," where an IoT class device is usually quiescent, waiting for something to happen, a sensor or timer triggering. When activity happens, you move from nanowatts of power to maybe a basic activity such as simple voice activity at 10µW to 30µW. Then you wake up other processors with a few mW of power for more complex recognition of phrases, then wake up the main application processor for full voice recognition, which wakes up the link to the cloud and spends the much higher amount of power needed to do that cloud application.

Cognitive layering

Cognitive layering for power.

"So when we talk about 'always on' what we means is 'almost always off'—that reflects the fact that you want to push the processing down the stack as far as possible and at the lowest level not even in processors at all. That's where the opportunities are," he said.


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