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The Memristor

The first new passive circuit element since the 1830s might transform computer hardware

Brian Hayes

Empire Building

Will the memristor turn out to be a transformative technology, the key to putting hundreds of trillions of devices in the palm of your hand? Or will we be asking, a few years from now, “Whatever happened to the memristor?”

The empire of the transistor has fended off many other rivals and would-be invaders. A memory technology based on magnetic “bubbles” floating on a garnet crystal once held great promise, but you can read about it now on the website of the Vintage Technology Association. The charge-coupled device, or CCD, was another candidate for main memory and mass storage; it failed to gain a foothold in that role, although it did find another niche, as the image sensor of digital cameras. And there were wilder flights of fancy, such as superconducting computers and photonic data processing.

This roster of defeated challengers might lead one to conclude that no innovation has a chance of displacing an entrenched technology. However, the transistor itself offers the obvious refutation. At its debut in 1948 it had to compete with the vacuum tube, which had dominated the electronics industry for 30 years. Although the transistor took more than a decade to establish itself, in the end the vacuum tube became a quaint collector’s item.

Today the TiO2 memristor is just one of many contending new technologies. Considering only the realm of switched-resistance memory elements, there are several other candidates, including devices based on phase changes, on magnetic fields and on electron spin. (Chua argues that all these devices should be classified as memristors.) To evaluate the long-term prospects of such technologies, one would have to go beyond basic principles of operation to questions of reliability, longevity, uniformity, cost of manufacturing and dozens of other details.

In a telephone conversation I asked Williams why he believes the memristor will be the technology that prevails. He offered several substantive arguments, but he also added, candidly: “It’s the one I’m working on. I have to believe in it.” In a sense this is the strongest endorsement anyone can give. As a bystander, I have the luxury of waiting on the sidelines to see how the contest comes out. But someone has to make choices, take risks and commit resources, or nothing new will ever be created.

©Brian Hayes


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