Memristors were conceived by electrical engineer Leon Chua in his seminal 1971 paper "Memristor--the Missing Circuit Element" (IEEE Transactions on Circuit Theory). His peer-reviewed claim startled electrical engineers by detailing how there was a "missing link" in circuit theory.
By mathematical necessity, according to Chua, a fourth passive electronics component--after resistors, capacitors and inductors--must exist. His argument was reminiscent of the inventor of the periodic table, Russian chemist Dmitri Mendeleev, who claimed that by mathematical necessity there were missing elements in the periodic table that must exist. Both were right. Mendeleev's missing elements were eventually discovered, and in 2006 Hewlett Packard Senior Fellow Stan Williams likewise discovered Chua's missing-memristor in a common semiconductor material.
Chua called his fourth passive circuit component a memristor, because it "remembered" the amount of current that had recently been flowing through it by changing its internal resistance--making it a memory-resistor. HP's formulation was titanium-dioxide, but since them many other semiconductor manufacturers have come forward to disclose that they had also been working on memristive materials in their efforts to build a universal memory type--called a resistive random access memory (ReRAM).
As a result, approximately 40 years after memristors were postulated by Chua, these materials are finally achieving widespread commercialization as universal memory chips that are nonvolatile, denser than flash, and yet faster than DRAM. A remarkable spectrum of semiconductor houses are promising memristive microchips, some as early as 2013, including Adesto Technologies, Elpida, Fujitsu, Global Foundries, Hewlett Packard, Hynix, IBM, Macronix, Nanya, NEC, Panasonic, Rambus, SanDisk, Samsung, Sharp, Sony, ST Microelectronics, Winbond, 4DS, and several research labs like IMEC collaborating with foundry partners like TSMC.
What you may not be aware of, however, is that the next 40 years are likely to be even more significant for memristors, as the basis of a new era of cognitive computers based on the architecture of the human brain. Spear-headed by the Defense Advanced Research Projects Agency (DARPA) program called Systems of Neuromorphic Adaptive Plastic Scalable Electronics (SyNAPSE) research labs are pioneering a new era of cognitive computers that are light years beyond artificial intelligence (AI). Participants included IBM, Hewlett Packard, and HRL Labs in cooperation with Boston University, Columbia University, Cornell University, Stanford University, University of California at Merced, and the University of Wisconsin at Madison.
Chua anticipated the application of memristors to artificial neural networks as far back as 1976 in his Proceedings of the IEEE paper Memristive Devices and Systems where he noted that the neuroscience standard model for neurons--the Hodgkin–Huxley model--was mathematically identical to a memristor.
It seems now that the fourth fundamental circuit element - referred to as the "memristor" - cannot exist in physical reality. In principle, no realistic physical model can be proposed for a solid state memory device which would operate in accordance with Chua's mathematical concept of genuine non-volatile memristors/memristive systems. When analyzed under physical aspects, the hypothetical mathematical state equations defining non-volatile memristors are by themselves in severe conflict with fundamentals of physics as discussed in "Fundamental Issues and Problems in the Realization of Memristors" by P. Meuffels and R. Soni (http://arxiv.org/abs/1207.7319) and "On the physical properties of memristive, memcapacitive, and meminductive systems" by M. Di Ventra and Y. V. Pershin (http://arxiv.org/abs/1302.7063).
The idea of a memory that is non-volatile, as fast as DRAM (I doubt the claim it is faster, the address logic will dominate that) and smaller is great. It is nice to hear that is coming. Of course, they said the same thing for FRAM.
However, people keep hyping this idea that we can mimic the human brain. Let's be clear about this:
- We don't know how the brain works. We know how one component, the neuron works. We don't have more than a tiny clue as to how that combines to make the neural part of a brain. The impact of the thousands of neurotransmitters and non-neural cells from a processing point of view is unknown. How can we mimic something we don't understand?
- We can't control an artificial brain, any more than we can control a human brain. How would you like to deal with a psychopath that is 10 times smarter than you, and thinks 1000 times faster? Until we understand this we'd better keep our neural network experiments very small scale.
Memristors have been conceived much Earlier than 1971, where only the name has been changed from "Memistor" bei adding an "r" behind "Mem". Stanford-Professor Bernie Widrow has founded the "Memistor Corporation" already in the early sixties. However, the implementation technology of this early memistor could not follow Moore's law.
The R & D smoking around the "memristor" stuff seems to be continuing in the New Year. That's really funny, because - up to now - no one has been able to show that Chua's hypothetical concept of nonvolatile memristor/memristive systems can be realized, i.e., to propose a reasonable physical model that would satisfy the mathematical state equations of such a system.
Memristor is just a component, like resistor, inductor or capacitor...saying it mimics the brain stretches reality too much...overall an exciting research component but we have not seen any commercial application from HP yet, still waiting for the memristor revolution!
David Patterson, known for his pioneering research that led to RAID, clusters and more, is part of a team at UC Berkeley that recently made its RISC-V processor architecture an open source hardware offering. We talk with Patterson and one of his colleagues behind the effort about the opportunities they see, what new kinds of designs they hope to enable and what it means for today’s commercial processor giants such as Intel, ARM and Imagination Technologies.