Researchers at Rice University, Houston, Texas have been working for nearly a decade on “inexact” computer chips. The chips are allowed to make a few mistakes within their operations, using less energy and less time compared with an accurate computation on a standard CPU. These new chips, with their less rigorous attitude to accuracy, have been tested by the researchers and can run seven times faster with 30 times less power usage than the chips upon which they are based.
Professor of Computer Science at Rice University, Krishna Palem uses an approach called “Probabilistic computing”. The researchers take existing computer chips and modify them. The chips are pruned of rarely used portions of their digital circuits. The circuits that do the least work or least important calculations can be removed or turned off to save energy and make them smaller.
Professor Palem said of his research; “When we first started working on this there was a large part of the world that was sceptical about what we were doing, but I can very confidently say that we are past that now.” The researchers presented their latest results and research paper at the ACM International Conference on Computing Frontiers in Cagliari, Italy last week.
What are these inexact chips good for? Project co-investigator Christian Enz explains “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.” The latest research results showed a chip with an average 0.25 per cent deviation from the correct value could cut energy consumption by 3.5 times. There are a large number of computer applications where small errors will not be noticeable by the average user including image, audio, video applications and search engine results. That’s a lot of overlap with applications that can use lossy compression.
Professor Palem says he expects the chips to be used in future mobile phones and hearing aids among other things. In fact these "inexact" chips are already available, incorporated into some computer devices. Now we know they are actually a component of the solar powered I-Slate educational tablet, designed for the Indian government school system.