But Professor Koomey's enthusiasm was reserved for a series of examples of how clever design can save power. The BigBelly trash compactor is solar powered and crushes waste to 20 percent of its original size. But the real innovation is that it sends a message when it is full allowing the trash collector to minimize collections. "Fewer truck trips means you are moving bits, not atoms," Koomey said.
He discussed wireless sensor motes that can be used to monitor city parking spaces powered by the scavenging energy from radio and television signals. The data is then used to drive street signs that direct drivers. Getting drivers parked quicker means less traffic and less gas consumption.
However, miniaturization and energy efficiency benefits are not automatic, Koomey cautioned. The good news is that, at the current rate of progress, we have until 2041 before we reach the Feynman limit of transistor-type action at the level of a single atom. However, long before that we will have to base integrated circuit operation and production on different principles, he said. The professor interrupted himself to make the observation that a research team drawn from Purdue University and the University of New South Wales has created a reliable single-atom device that uses electron-state switching to denote 1 and 0. The drawback today is that it requires liquid helium temperatures for operation.
The question remains, Koomey said: "Can we do better than historical trends? We could do worse especially if we do not address leakage current issues."
"Performance and efficiency are inextricably linked. We are still far from the theoretical limits. The future belongs to low-power systems," he concluded.
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Cell phones show a variety in talk time energy efficiency that is improving slowly, according to Professor Koomey.
The biggest problem today is heat extraction from inner layers. Once extracted to the surface, heat removal is no different from today's chips. But since the total system dissipation is significantly reduced from the 2D case, the overall system cooling requirements are reduced for the same design.
The physics of heat removal requires your conduction path not to heat up. So power line is not the way. You need something like the a/c where heat is extracted from the conduction path itself, by circulating cooling fluid, most simply air. But the power consumption for cooling must then be taken into account.
Good point @Zeev00, Feyman predicted that long time ago ("there is plenty of room at the bottom". Again using biological analogy: our brain is a 3D device...but we need to reduce power before going 3D, else there is no way to solve heat extraction problem...reducing computational accuracy, or moving to analog computing (as the brain does) would be useful to accomplish that...Kris
The only path to systematically reduce power seems to be to go 3D. I am not talking about the TSV 3D path, but the monolithic 3D one. With monolithic 3D integration the interconnects are shorter, and hence their capacitance and power; the off-chip drivers and their large power are gone; and heterogeneous integration saves yet another high-power chip-crossing signalling.
"Approximate data can reduce the computing load significantly. We have to start looking at the way we do computing from a system point of view." - I think is the key takeaway from that talk...our computing is too exact, we calculate everything with 32 or 64 bit accuracy...no need...look at our brains, work much better (pattern recognition for example) despite being much slower
Join our online Radio Show on Friday 11th July starting at 2:00pm Eastern, when EETimes editor of all things fun and interesting, Max Maxfield, and embedded systems expert, Jack Ganssle, will debate as to just what is, and is not, and embedded system.