
Memristors in silicon promising for dense, fast memory - ColinWright
http://www.bbc.co.uk/news/science-environment-18103772
======
haberman
Memristors promise to flatten part of the memory hierarchy, merging non-
volatile storage and RAM. But the interesting question to me as a systems
programmer is whether they will ever merge cache with everything else too.
This question is really important because if there were no cache there would
no longer be any benefit to compactness and locality in memory -- data
structures distributed across large areas of the address space would be just
as efficient as ones that are well-localized.

To be honest this idea worries me a little. The performance advantage of small
and local data structures is one of the main natural forces that encourages
software to be small and simple. Software tends to grow over time, both in
size and complexity, especially when more people are involved. Unchecked I
fear that there would be no natural counterbalance to this tendency.

Put another way, I'm actually a bit glad that Eclipse is horribly slow,
because it's an easy-to-observe symptom of the fact that it's a horribly
complex stack of software. If software like Eclipse could get by with
acceptable performance because it had fast access to vast swaths of memory, it
would be that much harder for an upstart competitor in this space (like Light
Table) to be disruptive, because Eclipise would perform well enough that
competing on speed doesn't impress.

I'm probably oversimplifying a bit, but I do think it generally good for
programmers when simpler software also has better performance naturally.

But even if Memristors could be as fast as SRAM, could you out enough of it
close enough to the CPU that it truly flattens the memory hierarchy
completely? This is where I hit the limits of my knowledge of computer
architecture.

~~~
Symmetry
Basically, we're never getting rid of the need for caches. You can't put
enough of it close enough to the CPU because the muxes needed to select the
data you need have too many FO4s[1] of fanning, and because you're limited by
the speed of light, and the arrays you need are too big to get all of them
close enough to the processor.

Another problem is write endurance. RRAM is expected to have be able to take
many orders of magnitude more writes before failing than Flash, but its still
limited. The fact that you have layers of SRAM cache between it and the
processor buffering against repeated writes to the same location is why I'd
still be comfortable using it as main memory. Otherwise you could get an
infinite loop that could actually damage the memory.

[1]<http://en.wikipedia.org/wiki/FO4>

~~~
juiceandjuice
You're neglecting the possibility that we abandon the Von Neumann architecture
altogether.

~~~
Symmetry
Quite true, but far out speculation about the future of computer architectures
doesn't really seem germane to talking about a new form of fast non-volatile
memory.

~~~
sliverstorm
It's just a popular sweet-nothing people have grown fond of parroting whenever
memristors come up. It is impossible to really refute, because it speculates
about the possibility of an architecture we haven't yet imagined. That plus
how cool "brand new architectures, completely new ways of computing!" sounds
to the layman, means you hear it every time the word "memristor" hits the
headlines.

The joke, of course, is that (if memory serves) modern computers actually use
the Harvard architecture- not Von Neumann.

~~~
haberman
When someone writes about the end of the Von Neumann architecture, I take it
as dreaming that the poster's favorite language will someday be faster than C.

~~~
swah
This reminded me of an old Yegge post:

"You do realize that John von Neumann spent the last 10 years of his life
singlehandedly developing a theory of computing based on cellular automata?
The computer you're reading this blog rant on was his frigging prototype! He
was going to throw it out and make a better one! And then he died of cancer,
just like my brother Dave did, just like so many people with so much more to
give and so much more life to live. And we're not making headway on cancer,
either, because our computers and languages are such miserable crap."

[http://steve-yegge.blogspot.com.br/2006/03/moores-law-is-
cra...](http://steve-yegge.blogspot.com.br/2006/03/moores-law-is-crap.html)

------
Symmetry
As awesome as RRAM is, and as much as I've boosted it in the past[1], there
are still lots of things that could go wrong. Unless its practical to
manufacture in large quantities, this won't go anywhere for instance.

[1][http://hopefullyintersting.blogspot.com/2011/12/resistive-
ra...](http://hopefullyintersting.blogspot.com/2011/12/resistive-ram.html)

~~~
mbenjaminsmith
I'm not sure why you left out R. Stanley Williams in your post there. Leon
Chua postulated the existence of a "4th" electrical component but didn't make
any progress on it himself.

Listen to Williams' main talk on YouTube. I'm pretty sure they've sorted out
how to manufacture memristor-based RAM -- and are licensing the process out
already.

~~~
anamax
See Williams ee380 talk as well - [http://www.stanford.edu/class/ee380/fall-
schedule-20112012.h...](http://www.stanford.edu/class/ee380/fall-
schedule-20112012.html) .

------
aidenn0
Anyone else find it a bit lame that they couldn't test switching time below
90ns with the excuse that they didn't have the equipment?

~~~
cheatercheater
No, because I don't understand the process they would need to measure, and
neither do you

------
zokier
Is there any info about discrete memristors, will there ever be such things,
or will all products be only integrated solutions? By discrete memristor I
mean part comparable to an individual resistor or transistor. Something
elementary, which the electronics-geek in me could play with.

~~~
hwillis
Memristor-like components have existed since 1960
(<http://en.wikipedia.org/wiki/ADALINE>). There is no demand for a discrete
component so I doubt anyone would start making them. You could make an
analogous device with a microcontroller, but that kind of defeats the purpose.
Anyway its an elementary circuit element, so its behavior is fully described
and not super exciting.

~~~
cheatercheater
Weren't those super-expensive? You know, the reason resistors are basic
elements is among others that they're cheap..

I think a simple SiO layer, which is what this newest memristor tech is based
on, could be super cheap.

Even if you can't build "big memristors", you could just parallel thousands of
them in a single package. Then, they would start being approachable.

Besides, tiny capacitance hasn't stopped anyone from using the likes of
varicaps, and huge inductance never stopped anyone from using an inductor.
They have their place.

I, for one, want to see a discrete Memristor in all shapes and sizes. If we
don't try it, and don't experiment with it, we might be shutting out 1/4 of
all electronics.

Luckily, a lot of electronics companies do feel their responsibility as
educators. That's why we have samples (I'll teach you to use my chip, and if
you become an important circuit designer you'll use my chips in your designs),
that's why we have lots of antiquated chips still in production (stuff like
OTAs which is of interest only to miniscule hobbyist groups), that's why we
can still buy devices in units.

I'm looking forward to it.

------
dwiel
I'm excited to see cheap memristor devices that provide access to their
computational ability.

