Scientists working at Hewlett-Packard have announced that they have discovered a fourth basic type of electrical circuit – one that might create a computer that "remembers" where it was and doesn’t need to boot up. 

Electronics theory recognizes three fundamental elements of a passive circuit: resistors, capacitors and inductors. Leon Chua, a scientist at U.C. Berkeley in the 1970s, posed that there should also be a fourth fundamental element known as a memory resistor, or memristor, and he proved the mathematical equations for it. A team of scientists at HP has now proven the existence of “memristance.”  The team, led by Stanley Williams, claims that memristance properties are very different from any other electrical device.  Williams and his team have developed a mathematical model and a physical example of a memristor, which they describe in the journal, Nature.

Williams compared memristor properties to water flowing through a garden hose. In a regular circuit, water flows from more than one direction. But in a memory resistor, the hose “remembers” which direction the water/current is flowing from, and it expands in that direction to improve the flow. Likewise, if water or current flows from the other direction, the hose/current shrinks from that direction.  According to Williams, "It remembers both the direction and the amount of charge that flows through it. ...That is the memory.”

It's very different from any other electrical device," Williams said of his memristor. "No combination of resistor, capacitor or inductor will give you that property." Williams and the HP team indicated that the memristor finding could lead to development of a new kind of computer memory that would not need to boot up. DRAM that is used on conventional computers is lost when power to a computer is turned off, and when the computer is turned back on it must be accessed from the hard drive.  But with the use of the memristor in a memory circuit the computer would not lose its place, even after the power was off and then turned back on.

According to Williams, "It's essential that people understand this to be able to go further into the world of nanoelectronics. It turns out that memristance, this property, gets more important as the device gets smaller. That is another major reason it took so long to find," Williams said.