Scientists develop new type of memory circuit

By Julie Steenhuysen

CHICAGO, April 30 (Reuters) - It took about 40 years to find it, but scientists at Hewlett-Packard (HPQ.N: Quote, Profile, Research, Stock Buzz) said on Wednesday they discovered a fourth basic type of electrical circuit that could lead to a computer you never have to boot up.

The finding proves what until now had only been theory -- but could save millions from the tedium of waiting for a computer to find its "place," the researchers said.

Basic electronics theory teaches that there are three fundamental elements of a passive circuit -- resistors, capacitors and inductors.

But in the 1970s, Leon Chua of the University of California at Berkeley, theorized there should be a fourth called a memory resistor, or memristor, for short, and he worked out the mathematical equations to prove it.

Now, a team at Hewlett-Packard led by Stanley Williams has proven that 'memristance' exists. They developed a mathematical model and a physical example of a memristor, which they describe in the journal Nature.

"It's very different from any other electrical device," Williams said of his memristor in a telephone interview. "No combination of resistor, capacitor or inductor will give you that property."

Williams likens the property to water flowing through a garden hose. In a regular circuit, the water flows from more than one direction.

But in a memory resistor, the hose remembers what direction the water (or current) is flowing from, and it expands in that direction to improve the flow. If water or current flows from the other direction, the hose shrinks.