2009 top underreported technology stories:5. Dumber may be smarter: Less-accurate chips bring more speed and savings on power and heat
A quiet revolution in integrated circuit technology is occurring in Texas. Researchers at Rice University in Houston have developed a new type of chip that uses just one-thirtieth the electricity and runs faster than comparable silicon produced using standard CMOS technology.
Is there a trade-off? Absolutely. PCMOS (probabilistic complementary metal-oxide semiconductor technology), as the new technology is called, is based on probabilistic logic, which by definition is less accurate than the Boolean-based logic we all learned in school and that is the basis of the calculating algorithms used by conventional microchips.
[ 2009's major chip story: "ARM versus Atom: The battle for the next digital frontier" ]
That may sound counterintuitive. After all, who wants a computer that doesn't return accurate information? But before you click to the next page, consider this: Applications such as random number generation used for encryption, video playback on handheld devices, and signal processing don't have to be completely accurate, says Krishna Palem, a professor of computer science at Rice. "If we are willing to live with a tiny bit of error, there are significant savings in power," he says.
Palem explains that the movement of electrons in a chip produces "noise" that interferes with accuracy at the transistor level. To overcome that noise, most chips run at a relatively high voltage. A lower voltage means more noise and less accuracy, but decreased power consumption and heat.
How much of a problem is decreased accuracy? To paraphrase the researcher, "not all calculations are created equal." Pick a four-digit number -- say, 2143. In a calculation, the values of the thousands and hundreds places are quite significant, the tens place less so, and the ones place the least significant. So PCMOS lowers the operating voltage of the logic gates that calculate the least significant bits. In a video application, PCMOS might cause a degradation of quality too small for most people to discern. Used in a cell phone, the savings in power could mean battery life measured in weeks.
Despite the seemingly radical nature of PCMOS, devices made on this technology can be produced using conventional fabricating techniques and materials, says Palem. Indeed, samples have already been produced by Taiwan Semiconductor Manufacturing.
The first samples were ASICS used for encryption; in the near future, Palem, whose team includes graduate students at Rice and researchers at Singapore's Nanyang Technological University, will be conducting proof-of-concept tests on microchips for Bluetooth headsets, graphics cards, hearing aids, medical implants, and eventually cell phones. He expects to see some actual production in 2010.