The Memristors Are Coming:
The nanotech world is abuzz over a recent announcement that HP will partner with semi manufacturer Hynix to bring memristor memory devices to market within 3 years.
Such a development would be unprecedented. So far, no single component has been able to replace both DRAM and flash. DRAM is cheap but volatile, meaning it loses data when the power is turned off. Nonvolatile flash memory, by contrast, doesn’t need power to retain its data but is too expensive for the volume necessary for main hard disks. (Right now, 250 gigabytes of DRAM costs US $60, but the same amount of flash memory will set you back almost $800.)
In both kinds of memory, data is stored as charge. The problem is that the envelope for the electrons that constitute a discrete charge can’t be made much smaller. That makes it difficult to squeeze more memory into the same size footprint for the same cost. (IEEE Spectrum)
What the Heck is 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. (Cosmic Log @ MSNBC)
Memristors, like capacitors, inductors, and resistors are passive devices. Passive devices don’t introduce additional energy into a circuit and they don’t have gain — the only energy they need to operate is the signal itself (unlike active devices, which need additional current for biasing, amplification, etc.) They “record” data by having a resistance that changes depending the direction and intensity of current flowing through them. When the current stops flowing, the resistance (high or low in binary, for example) remains in the last state it was in indefinitely, until current is again applied.
Why You Should Care:
Memristors represent a new, all-purpose form of memory that has the non-volatility of flash combined with (eventually) the low cost and speed of DRAM. The other thing memristors have going for them is that they do not store data as charge, and they require a minimum amount of charge to read from and write to, compared to current techs. This translates to lower power requirements (you no longer have to dedicate some portion of your supply to keeping DRAM alive during operation) and denser memories (you no longer have a minimum footprint dictated by the actual size of the electrons comprising the stored charge).
At the moment, it appears HP will be marketing discrete memory modules with this technology, but it is only a matter of time before memristive memory (or Resistive RAM, as HP calls it) is deployed within larger types of circuits, including microcontrollers. Lower power, smaller MCUs with bigger, faster program memories mean smarter, wireless embedded devices. There are still many hurdles to get over before we attain a true Internet of Things, but memristors represent another small step towards a culture of spimes.
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