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Researchers rescue Moore's Law

Will memristors save Moore's Law? The answer appears to be yes … that is, if you redefine Moore's Law, which has fueled the growth of the computer industry for four decades. Research groups say that memristors, a new type of memory device that's on the verge of going commercial, will dramatically enhance the storage capacity and usability of computers.

HP, the world's top PC manufacturer, today announced a collaboration with memory-chip maker Hynix to get the first memristors to market in three years. One of the first goals will be to create a computer you can "turn on and off like a light bulb," said Stan Williams, founding director of HP Lab's Information and Quantum Systems Laboratory. But that's just the beginning.

HP isn't the only company joining the memristor revolution: IBM and Samsung have also looked into the technology, and in the journal Nano Letters, Rice University researchers today report the development of silicon-based memristors that they say will extend the limits of circuit miniaturization for years or even decades to come.

Moore's Law, first described by Intel co-founder Gordon Moore in 1965, says the number of transistors that can be squeezed onto an integrated circuit at least doubles every two years. Memristors haven't yet been developed to the point where they can take the place of transistors, so they don't fit the standard definition for Moore's Law acceleration. But they can make more efficient use of standard silicon-based processors and could eventually take over the processing job as well, based on HP research that was published in Nature this year.

"Moore's Law in itself has evolved and morphed in time," HP's Williams told me today. "It used to be the number of transistors in a chip, but now it means exponential growth in capability on a chip. ... I personally don't see any need for this exponential increase in capability to end within the next few decades."

The current frontier in memory storage is flash memory, which is used in some computers as well as in cameras and key-chain thumb drives. Flash drives work well enough for today's applications, but they're beginning to approach their physical limits for memory storage. "Manufacturers feel they can get pathways down to 10 nanometers," Rice University Professor James Tour explained in a news release. "Flash memory is going to hit a brick wall at about 20 nanometers. But how do we get beyond that? Well, our technique is perfectly suited for sub-10-nanometer circuits."

Williams said HP's goal is to have memristors that double whatever the bit density of the best flash memory is in 2013, which he acknowledged was "a moving target."

So what's a memristor?
Memristors, or "memory resistors," take advantage of the fact that passing electrical current through particular types of material will change the molecular structure of that material so that it "remembers" which way the current was running, and at what voltage, even when the power is turned off.

Memristors are said to represent a "fourth class" of basic electrical circuit, alongside resistors, capacitors and inductors. The concept behind memristors was first proposed in 1971 by circuit theorist Leon Chua, but for decades it was nothing more than a concept.

"It was only two years that we essentially announced that memristors were real, that they're more than a theoretical prediction," Williams said. "To me, it's so amazing that this concept lay dormant for nearly 40 years."

Memristors are built up from tiny sandwiches of thin-film circuitry. HP's experimental devices, for example, use a layer of titanium dioxide with wires that are about 50 nanometers wide. The silicon-oxide circuitry being developed at Rice contains nanocrystal wires as small as 5 nanometers. Layers of nanocircuit sandwiches can be stacked up to create three-dimensional memory arrays.

The result is that huge amounts of data can be retained inside your computer in an instant-on, instant-off mode, with much less energy required for operation.

Where the technology is going
Williams said HP will work "shoulder to shoulder" with Hynix over the next three years to turn memristor technology into a new type of computer chip called Resistive Random Access Memory, or ReRAM. Such chips could replace the flash memory currently used in mobile devices and music players, as well as DRAM chips and hard drives in computers.

Meanwhile, in Texas, the Austin-based tech design company PrivaTran is testing a 1-kilobit silicon-oxide chip developed through a collaboration with the Rice University researchers. The company says it is using the technology in several projects supported by the Army Research Office, the National Science Foundation, the Air Force Office of Scientific Research and the Navy Space and Naval System Command's programs for small-business innovation and technology transfer.

"We're real excited about where the data is going here," Rice's news release quoted PrivaTran CEO Glenn Mortland as saying.

Once memristors really take hold, consumers may well think of their computers in a completely different way, HP's Williams said. "We do see terabyte thumb drives — multiple terabytes — as being possible," he told me. "You can think about storing lots and lots of high-def video, you can think about storing 3-D video. That's something that's coming down the pipe."

Even processing 3-D video will require quick access to huge amounts of data, he noted. "You have to have something [for memory storage] that's very dense but also very fast," he said. "You have to be able to write to it very, very fast, and you need to be able to do it without the thing burning up."

Thanks to the research being done at HP and elsewhere, memristors could someday do the processing as well.

"I think that the memristor is the gift that's going to keep on giving," Williams said. "I do believe that about 10 years from now we will see memristors used in some type of logic. Either standard logic ... or there's another type of logic that memristors are capable of, and that's what we call synaptic logic. The type of logic that brains use."

Did I just feel a chill? Is this the beginning of the rise of the machines? Or do you suspect that the hype is being laid on more than a few nanometers thick? Feel free to weigh in with your thoughts about the memristor revolution in the comment space below.

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