Revolutionary microchip uses 30 times less power

In the first real-world test of a revolutionary type of computing that thrives on random errors, scientists have created a microchip that uses 30 times less electricity while running seven times faster than today’s best technology.

The U.S.-Singapore team developing the technology, dubbed PCMOS, revealed the results Feb. 8 at the International Solid-State Circuits Conference, the world’s premier forum for engineers working at the cutting edge of integrated-circuit design.

Conceived by Professor Krishna Palem, PCMOS piggybacks on the “complementary metal-oxide semiconductor” technology, or CMOS, that chipmakers already use. They will not have to buy new equipment to support PCMOS, or “probabilistic” CMOS. Although PCMOS runs on standard silicon, it breaks with the past by abandoning the set of mathematical rules—Boolean logic—used in all digital computers. PCMOS instead uses probabilistic logic, developed by Palem and postdoctoral research associate Lakshmi Chakrapani.

“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.

Silicon transistors become increasingly “noisy” as they get smaller, but 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 consequently more power-hungry.

“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.”

PCMOS was jointly validated by Rice and Nanyang Technological University (NTU) in Singapore via a joint institute Palem founded in 2007, the Institute for Sustainable Nanoelectronics (ISNE). Directed by Palem, ISNE is based at NTU, where prototype PCMOS chips were manufactured last year.

The prototypes were application-specific integrated circuits, or ASICs, designed solely for encryption. Unlike the general-purpose microprocessors that power PCs and laptops, ASICs are designed for a specific purpose and are “embedded” by the millions each year in such products as automobiles, cell phones, MRIs and electronic toys.

Palem said PCMOS is ideally suited for encryption, a process that relies on generating random numbers. It also works with 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 images looking as good with a calculation that’s only approximate.

Jade Boyd, Rice News