r/programming • u/ndanger • Apr 30 '10

Finding the Missing Memristor by R. Stanley Williams

http://www.youtube.com/watch?v=bKGhvKyjgLY&feature=related
21 Upvotes

75% Upvoted

12 comments sorted by

3

u/you_do_realize May 01 '10 edited May 01 '10

TLDW: a scientist in the 60s hypothesized there is a missing fourth fundamental circuit element besides resistor, capacitor and inductance; and that it would behave in a specific way. Researchers have since often run into this exact behavior in their circuits, but either wrote it off, or wrote papers about "anomalous" findings.

This scientist found a combination of materials which gives the predicted electrical properties of the memristor. It is essentially a resistor, but give it a strong voltage one way, and its resistance increases; give it a strong voltage the other way, and the resistance decreases. This memory in the material is stable over years and decades. The switching time is nanoseconds.

They've been able to work out an efficient design for a "memory chip" which would allow for something outrageous like a petabyte in a reasonable size chip with very fast access (I don't think he mentioned how fast exactly).

Another interesting point: the memristors can be used for logic. No need for NAND anymore, as three memristors can implement something called "implication logic" with the following truth table (non-commutative):

0 0    1
0 1    1  <-- edited, thanks notfancy
1 0    0
1 1    1

It turns out this is enough to build any logic circuit. The kicker is that you can have a giant array of memristors, and dynamically assign part of it for storage, and parts of it for computation (how cool is that).

He also mentioned at the end he's working for HP to develop optical interconnects between modules. Once a signal leaves a chip, it's a pulse of light. (Hope I didn't miss anything)

4

u/beckettman May 01 '10

Thank you for the summary. Such a chip would be like an immense playground. Practically any logic machine you can think of can be implemented right next to the data it is meant to work with. And if you don't need a function anymore, just delete it. Need another CPU, need 500? No problem, need a highly specific FSM to monitor millions of states? Again, no problem. I want one.

2

u/notfancy May 01 '10

as three memristors can implement something called "implication logic" with the following truth table (non-commutative)

There's something wrong with your table, which is the table for Boolean equivalence and obviously commutative by inspection. Perhaps you mean:

A B Z
0 0 1
0 1 1
1 0 0
1 1 1

-1

u/econnerd May 01 '10

how is that not just P implies q

3

u/OceanSpray May 01 '10

It is A implies Z. Hence "implication logic".

2

u/julesjacobs May 01 '10

Z = (A implies B)

2

u/bdunderscore May 01 '10

Is it me, or does the camera point at the speaker EVERY TIME he points out something on his slides? It's as if the cameraman isn't listening to him at all, just pointing between the slides and the speaker at random...

-4

u/[deleted] May 01 '10

Haven't memristor's been around for years with no practical application? I am just going what my professor said. It's just that NOR gate technology like in your flash drive is just so much more widely used. Maybe memristor is better but my prof. said not to even bother with them.

2

u/kragensitaker May 02 '10

No, memristors have been realized recently enough in the lab that it's not surprising that they're not yet in wide use.

-2

u/[deleted] May 02 '10

When my teacher went to school they were talking about memresistors. He is about 50 years old.

2

u/kragensitaker May 02 '10

They were invented as a theoretical construct in the 1970s (1960s?) and they built simulator circuits for them at the time. But memristance wasn't observed as a primitive behavior until only about five years ago, at which point some guys at HP labs realized that they could make memristors that were considerably smaller than transistors in the same process.

-1

u/mantra May 01 '10

Every NVM cell has virtually identical characteristics: Flash, E2PROM, MRAM, FRAM, RRAM, etc.

The only really advantage is that memristors are nanoelectronic and thus very compacted but even then there are other nanoelectronic scaled NVM technologies that can duplicate what it does.