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Seeking the Fourth Circuit Element

F.Y. Teng | May 25, 2010
A conversation with the czar of R&D at HP Labs about taking memristors from paper to production to mobile computers to enterprise infrastructures.

Memristors (a contraction of memory resistors) first appeared in a paper published in 1961 by Professor Leon Chua from the Electrical Engineering Department of UC Berkeley in California, the US. In the paperMemristorThe missing circuit element (IEEE Trans. Circuit Theory CT-18, 507-519 (1971))proved a number of theorems to show that there was a 'missing' two-terminal circuit element from the family of "fundamental" passive devices:  resistor, capacitor and inductor (e.g. elements that do not add energy to a circuit), according to an explainer on the HP Memristor FAQ page.

He proved that no combination of nonlinear resistors, capacitors and inductors could duplicate the properties of a memristor. The most recognisable signature of a memristor is that when an AC voltage is applied to the device, the current-voltage (I-V) plot is a Lissajous figure (the curve formed by combining two oscillations that are perpendicular to each other). The most commonly observed I-V trace is a 'figure 8', or a 'pinched loop' for which the current is zero when the voltage is zero.  This inability to duplicate the properties of a memristor with the other passive circuit elements is what makes the memristor fundamental, said the FAQ, which also went on to describe just what a memristor is. An ideal memristor is a passive two-terminal electronic device that is built to express only the property of memristance (just as a resistor expresses resistance and an inductor expresses inductance).

A good three decades after Prof. Chuas paper was first published, chief researchers at HPs Information & Quantum Systems Lab announced (on the week of April 8) what it called another significant advance in memristor research: they could get memristors to perform logic functions. And, if memristors can perform logic, they might one day be used to create computer processors…and since those processors could be made with industry-standard materials and processes, memristors might help extend Moores Law past the point where silicon technology runs up against insurmountable technical barriers, said Stanley Williams, Senior Fellow and Founding Director of the Information & Quantum Systems Lab (pictured above, photo courtesy of HP), in an article published on the HP website.

Williams went on further to say that he expected to see memristors used in computer memory chips within the next few years, and that in fact, HP Labs already had a production-ready architecture for such a chip.

We at Computerworld Singapore recently spoke with Stanley Williams, hoping to understand the full import of HP Labss work with memristors to date.

Computerworld Singapore: What does this technology mean for IT people and their enterprise?
Stanley Williams:
Well, in terms of the enterprise, one of the major problems that were having is that the gap between memory and storage keeps on getting wider and wider. If you think about Cloud computing, if you think about all of the types of services that are on the Web, they are all very, very data heavywhich means that we have to be doing a lot of look-ups, going out and finding data and bringing it back to the processor chips or bringing it to the memory. So spinning disks arent getting any faster, whereas memory is trying to get faster, thus we have this big bottleneck between memory and hard disk thats getting wider and harder to cross.


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