Chip drops Boolean logic, runs seven times faster

  • San Francisco (CA) – Researchers at Rice University developed a new microchip that promises to run seven times faster and consume 30 times less electricity than today’s “best technology”. The project, which is supported by Intel and the Defense Advanced Research Projects Agency could result in new processors for cellphones that would enable users to recharge their phones not every few days, but every few weeks, the scientists said.

    The new processor shown discussed at the International Solid-State Circuits Conference (ISSCC), uses common CMOS technology, but drops Boolean logic mathematical rules and adopts probabilistic logic, a new form of logic developed by Rice University professor Krishna Palem and his doctoral student, Lakshmi Chakrapani.

    Called PCMOS, the chip runs on standard silicon, which means it can be produced with standard chip manufacturing equipment. Palem claims that the use of probabilistic logic results in 30 times less power consumption and an overall increased speed of 7x.

    "A significant achievement here is the validation of Rice's probabilistic analogue to Boolean logic using PCMOS," said Shekhar Borkar, an Intel Fellow and director of Intel’s Microprocessor Technology Lab, in a prepared statement. "Coupled with the significant energy and speed advantages that PCMOS offers, this logic will prove extremely important because basic physics dictates that future transistor-based logic will need probabilistic methods."

    In contrast to Boolean logic chips, Palem said it is possible to actually use the errors in his chip: Silicon transistors become increasingly 'noisy' as they get smaller and engineers have historically dealt with this by boosting the operating voltage to overpower the noise and ensure accurate calculations. Chips with more and smaller transistors are more power-hungry as a result.

    "PCMOS is fundamentally different," Palem said. "We lower the voltage dramatically and deal with the resulting computational errors by embracing the errors and uncertainties through probabilistic logic."

    Palem said that prototype application-specific integrated circuits, or ASICs using the technology have been built already. He believes that “PCMOS is ideally suited for encryption, a process that relies on generating random numbers. It's equally well-suited for graphics, but for different reasons. In a streaming video application on a cell phone, for example, it is unnecessary to conduct precise calculations. The small screen, combined with the human brain's ability to process less-than-perfect pictures, results in a case where the picture looks just as good with a calculation that's only approximately correct.”
    The scientist promises that if PCMOS can be used for embedded ASICS, the drop in power consumption in devices such as cellphones or medical devices can be significant: “For consumers, it could mean the difference between charging a cell phone every few weeks instead of every few days. Globally, that would help reduce the information technology industry's carbon footprint.”

    Palem said he hopes PCMOS technology will enter the embedded computing market in as little as four years.

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