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Prototypes of a new computer chip recently unveiled at the ACM International Conference on Computing Frontiers are 15 times more efficient than equivalent chips made using current production technology, promising major power reductions and extended battery life for portable devices. But these efficiency gains didn’t come without a price: the chips make occasional errors.
Though the concept is deceptively simple, a research team with members from Rice University in Houston, Nanyang Technologies University in Singapore, the Center for Electronics and Microtechnology in Switzerland, and the University of California, Berkeley, has been working on the project since 2003. The goal was to get “inexact” chips that use less power by making a few mistakes in calculations. By managing the likelihood of errors and limiting which calculations create errors, researchers found they can cut energy demands while boosting performance.
One approach eliminates rarely used portions of digital circuitry. The first pruned chips were twice as fast, half the size, and only needed half the energy of their more-accurate, intact cousins.
Another approach uses a technique called confined voltage scaling. It takes advantage of processing speed to cut power demands. Tests show inexact chips with an average 0.25% error rate cut energy demands by a factor of 3.5 compared to traditional chips. That factor could rise to 15.
Obviously, high-error rates would not work well in an engineering environment. But processing a photo is another matter. There, small errors are ignored by the human eye. For example, it was found relative errors up to 0.54% were almost indiscernible while rates up to 7.5% still produced discernible images. Initial uses for the pruning technology will most likely be in application-specific processors embedded in hearing aids, cameras, and other electronic devices.
The inexact hardware is also key to a new educational computer tablet called an I-slate. The I-slate is for classrooms in India with no electricity and few teachers. The low-power needs of the pruned chips should let the I-slate run on solar panels similar to those in handheld calculators. The first I-slates are expected to go on sale next year.
