"Inexact" Computer Chip is 15X More Efficient By Making a Few Mistakes

inexact chip© Avinash Lingamneni/Rice University/CSEM

Researchers at Rice University have unveiled a computer chip that is at least 15 times more efficient than today's technology and it achieves that efficiency through a surprising design. Most research is focused on making computing technology as accurate as possible, but the team turned that around and designed an "inexact" chip that occasionally makes errors, leading to not just better energy efficiency, but better processing performance too.

How can a computer chip that makes mistakes be better? Well, the team was able to manage the probability of errors when designing the chip and limited which calculations could produce errors. Rice University explains that by "pruning" away rarely used parts of digital circuits on a microchip, they were able to boost speed, cut energy use and make a chip that was about half the size of traditional microchips, while accepting a certain amount of errors.

“In the latest tests, we showed that pruning could cut energy demands 3.5 times with chips that deviated from the correct value by an average of 0.25 percent,” said study co-author Avinash Lingamneni, a Rice graduate student. “When we factored in size and speed gains, these chips were 7.5 times more efficient than regular chips. Chips that got wrong answers with a larger deviation of about 8 percent were up to 15 times more efficient.”

Project co-investigator Christian Enz, who leads the CSEM arm of the collaboration, said, “Particular types of applications can tolerate quite a bit of error. For example, the human eye has a built-in mechanism for error correction. We used inexact adders to process images and found that relative errors up to 0.54 percent were almost indiscernible, and relative errors as high as 7.5 percent still produced discernible images.”

inexact chip demo© Rice University/CSEM/NTU

This image above shows frames produced with video-processing software on traditional processing elements (left), inexact processing hardware with a relative error of 0.54 percent (middle) and with a relative error of 7.58 percent (right). The inexact chips are smaller, faster and consume less energy. The chip that produced the frame with the most errors (right) is about 15 times more efficient in terms of speed, space and energy than the chip that produced the pristine image (left).

The inexact chip will find its way into applications where special-purpose embedded microchips are used, like hearing aids, cameras and other small electronics by 2013. Inexact hardware is also being used in the I-Slate educational tablet, which was designed for Indian classrooms with no electricity. Their small power requirement will allow them to run on small solar panels like those used on calculators. There are plans to get 50,000 I-Slates into classrooms in India over the next three years.

"Inexact" Computer Chip is 15X More Efficient By Making a Few Mistakes
Researchers have designed a microchip that is faster, smaller and far more energy efficient by allowing it to make occasional errors.

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