Memristance is futile. Not.

I came across this wired article recently, and what I read sounded too science-fiction-y to be true, so then I decided to go to the source, and found this video (see below) by a researcher at HP, and it turns out to be both true and “science-fiction-y”.

We are used to thinking in terms of standard circuit elements — resistors, capacitors, inductors. One establishes a relationship between voltage and current, the second better voltage and charge, and the third between magnetic flux and current.

Now it never occurred to me to really think about it this way (it’s one of those things that’s only obvious in hindsight), but there is a missing piece of symmetry here.

Look at that list again, and it might jump out at you that among current, voltage, charge and magnetic flux, they’re related in pairs to each other, with the exception of charge and magnetic flux. Seeing this now, it might be reasonable to speculate on another circuit element that should do precisely that. And indeed someone did, about forty years ago, and named the missing piece the memristor.

Now I should acknowledge that there is a bit of controversy whether what HP labs claims to have discovered really matches up with this idea, so we’ll just have to wait a few years to test these claims, since the first commercial applications of this technology won’t be out for another five years at least.

But let’s continue. One of the observations made in the video linked I above is that the memristance obeys an inverse square law. This means the tinier the dimensions, the greater the observed effect. Which also means this is something that would belong purely in a chip, and not something you’d be putting on a breadboard any time soon.

The most exciting property, though, is that it’s behavior in the future depends on its past. So it is both a logic component as well as a storage component. So you could build a dense cluster of these things and determine which parts do what function, in a configurable sense, much like an FPGA on steroids.

I used to think (again, only because this is what I was taught) that the fundamental logic component was a NAND gate — but this turns out not to be true. Instead, it turns out that if we consider the interaction between input A and input/output B expressed using memristors, as an IMP gate, then we can construct a NAND gate out of these.

Further, multiple layers of these memristors can be stacked above a conventional CMOS layout, and densely packed together, leading to unprecedented on-chip memory, perhaps on the order of petabits!

So, how would this change things? It would certainly deprecate the SRAM ->DRAM->Hard Drive pyramid of caches we have right now, and we would not only have an ocean of universal memory, but our processing elements would be floating on this ocean, and entirely commingled with it!

We certainly won’t need to deal with the Von Neumann bottleneck any more …


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