Shades Of Green

What is considered green today as it relates to SoCs means different things from different perspectives, but all of it could have big implications for the Internet of Things.


By Ann Steffora Mutschler

Ask five people in the electronics industry what ‘green’ means and you are sure to get five different answers. In the datacenter, the definition is a little clearer because big iron draws so many amps. But at the SoC level where does the industry stand?

The answer is as multifaceted as an SoC itself, with some answers based more on one-upmanship than real metrics.

Chris Rowen, a Cadence fellow and CTO of Tensilica, sees at least three dimensions of what people mean when they talk green. “Everyone who is working on either improving functionality (that’s green No. 3), or improving cost (green No. 2) is typically very happy to wrap themselves in the robes of moral superiority, which is green No. 1. There are lots of reasons to do it in many products quite apart from moral superiority, so it’s going to happen regardless.”

One interesting correlation that comes out of the green discussion is that almost everything done to reduce power dissipation in a chip or a system also tends in the long run to make it cheaper, Rowen noted. “In the data center it is pretty obvious because people understand just what the cost of cooling is. Getting power in, getting heat out is a significant fraction of the total operating cost of these things. But in almost any kind of product, if you cut down the power you have less heating, which means that your circuit runs faster, which means you can, in some cases, use simpler circuits and take less area or you don’t spend as much money on the packaging. Lots and lots of positive feedback loops work in the relationship between cutting power and cutting cost. Everybody can agree with one or the other. That’s certainly a big part of green.”

Put in perspective on a global scale, power dissipation in electronics is a very small percentage of the overall energy use. “You’re talking about modest single-digit percent of electricity consumption, and electricity is only a fraction of energy consumption,” Rowen said. “So the really big impact is what can more intelligence in products do to reduce non-electronic energy consumption? How do I make my appliance smarter? It isn’t that I reduce the power in the electronics that control my washer, it’s how do I control the motors, the time it runs and manage the standby and all of those other things that probably have the biggest effect on total energy consumption. Carbon footprint doesn’t come from the power of electronics itself. It comes from the smartness of the engineering inside as to how you can be more miserly in power.”

Patrick Groeneveld, a scientist in the implementation group at Synopsys, agreed. “There has never really been a good definition for it. It has been almost a sales pitch sometimes. What it means for true engineers is just to be very efficient and not wasteful. That’s what good engineers do all the time by the way—we make these tradeoffs between using our energy in the most effective way.”

He noted that there are two angles to the green definition. “The first angle is just being very efficient. The second is to do it very smart, and that ties into efficient as well. In terms of ‘efficient’ you can think about a traditional light bulb was 5% effective. Now we can get much higher efficiency with LED lights. Similar things are happening thanks to Moore’s Law on chips and SoCs as well. The boost that we got every year for chips thanks to Moore’s Law was that as these transistors take less energy to switch, meaning we can do more work for less energy, or the same work for less energy. That has been going on for the past 50 years.”

However, he pointed out that every time we reap this benefit we start wasting the energy again on all kinds of cool features. “If you’ve noticed, the battery life of your phone didn’t really increase even though we put much better chips in it than in past years. It is mainly too because we’ve added all these cool features, so we immediately spent all the energy that we gained on features. There is a very interesting law—it’s the law of perceived usability. We need exponentially more transistors for the consumer to perceive a slight improvement or linear improvement in features of their cell phone.”

Location, location, location

Geography also plays into the definition of ‘green.’

“In the United States, the political environment leads into the business environment and so green is not seen as cool,” said Karl Freund, worldwide vice president of marketing and end user business development at SoC developer Calxeda “It’s not seen as an imperative or a mandate to be socially responsible. Europe is different. In Europe, whether in some cases it’s legislated or incentivized or just to be a responsible corporate citizen and avoid the devastation of the Black Forest—they’ve taken it very much to heart. If you look at universities, research centers, big pharma or big engineering, automotive and so forth, they are very green. It’s very cool to be green in Europe. It’s not cool to be green here. In China it’s an imperative, but for economic reasons—they just can’t build power plants as fast as their information economy is growing, so they are concerned about power as a limited resource. It’s interesting because you have three different economies all treating it differently, but they all have the same need. In North America it’s really a secondary consideration for most people. They’re just trying to get as much horsepower per dollar in the data center. They’ll say they are concerned, but do they really drive their purchasing decisions based on it?”

Still, the writing is on the wall that being green will be required. “They all know that they’ll eventually have to do something because you reach a point of inability to get that much power into a rack, and so rack-level power in a lot of data centers is still 4 kW,” he said. “Not everybody can be like an eBay or Amazon and have 15, 20, 30 kW in a rack because those are very expensive data centers. Those are $200 million data centers. The guys who pay the most attention to power in North America are the ones with really big infrastructures in North America—the Googles, the Facebooks, the LinkedIns, the eBays, the Amazons, Microsoft, AT&T.”

Internet of Things

Where ‘green’ starts to resonate in the chip and SoC realm is when the discussion turns to the Internet of Things, according to Qi Wang, technical marketing group director at Cadence. “Once you get down to the Internet of Things then green technology really make sense.”

He related a real-world example to illustrate the potential of the Internet of Things. He recently upgraded his swimming pool pump to a new variable speed pump and has already noticed a savings in electricity costs. “This makes me think if this variable speed pump in the future is part of the Internet of Things, there will be even more money savings because right now it just depends on the water sensing. But in the future it could adjust the speed with a human in the pool, with the temperature or with other devices. It may talk with the smart meter to do the adjustment so there’s a lot of potential. And if your refrigerator becomes part of the Internet of things in a home network, if your dryer or even your oven is smarter, all those things add up. That will not only save on household bills, but will save the whole society in terms of power consumption.”

To enable the Internet of things, there are standards coming up to support energy efficient communications such as Bluetooth low energy (BLE) also referred to as Bluetooth SMART and Zigbee Alliance. In the automotive space, a local area network for automobiles is being standardized, around which Cadence has developed IP.

Another factor in the Internet of Things is energy-harvesting technology, which will be needed to support devices that are deployed as part of near-threshold or sub-threshold computing. The research institute IMEC has been working on energy harvesting for many years.

The question is no longer ‘how’ but ‘when’ the Internet of Things will bring ‘green’ to bear in the semiconductor space. The work is happening and innovation is around every corner.

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