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MIT Reports 400 GHz Graphene Transistor Possible With 'Negative Resistance'
An anonymous reader writes "The idea is to take a standard graphene field-effect transistor and find the circumstances in which it demonstrates negative resistance (or negative differential resistance, as they call it). They then use the dip in voltage, like a kind of switch, to perform logic. They show how several graphene field-effect transistors can be combined and manipulated in a way that produces conventional logic gates. Graphene-based circuit can match patterns and it has several important advantages over silicon-based versions. Liu and co can build elementary XOR gates out of only three graphene field-effect transistors compared to the eight or more required using silicon. That translates into a significantly smaller area on a chip. What's more, graphene transistors can operate at speeds of over 400 GHz."
... they want their GHz war back...
...graphene saves the world, creates amazing superproducts, and almost defies the laws of physics.
Cynicism aside, the research is exciting, but it's not likely to bear fruit any time soon.
Great warrior...hrmph! Wars not make one great.
k.T.
http://xkcd.com/678/
"in which it demonstrates negative resistance (or negative differential resistance, as they call it)"
Negative resistance and negative differential resistance are not the same thing. Negative resistance would mean the current flows against the voltage. Negative differential resistance just means that the current goes down when you increase voltage.
The first one is not possible (unless you've got an external energy source driving the current) because it would imply a perpetuum mobile. The second is unusual, but doesn't violate any fundamental laws of the universe.
Don't worry. They'll build Graphene GPUs at the same time as they build CPUs out of them. I'm still waiting for the low power, sunlight readable, full color displays to come out.
When our name is on the back of your car, we're behind you all the way!
When your DRAM still has nanosecond-level access times, it's still pretty relevant.
And what prevents silicon transistors from operating at frequencies over 400 GHz in theory? I'd much very like to know the answer before gasping in excitement. Something is telling me this estmiation has very little to do with the current technological level we have now...
Given the early state of this technology, it could well be that this technology doesn't get into your computer until the time it would match Moore's law (ignoring of course, that Moore's law deals with transistor size, not clock speed).
"First they came for the slanderers and i said nothing."
Two NMOS transistors and a resistor can perform an XOR in Si. I remember interviewing at Intel in 1980, and every damn interview question was about XOR gates. First was an XOR gate in TTL, then an XOR gate in CMOS, and finally an XOR gate in NMOS. Apparently I passed all three questions, 'cause they offered me a job.
I suspect they wont immediately. More likely they will cut costs and instead of having 4 or 8 cores on your CPU, you'll have ONE, just clocked higher. a single core is a LOT less complex to program for, and it will run fast enough that it doesn't matter for some time. ditto for GPUs. I suspect you'll see the designs simplified, consuming less power, etc long before we see similar complexity designs to today on graphene.
A major reason is that the software just isn't there yet.
I run: Windows, OS X, Linux, FreeBSD. Just because you have a hammer, doesn't mean everything is a nail.
MIT may have reported it, but the research comes out of UC Riverside. Give credit where credit's due; interesting research isn't only done at MIT, Stanford, or Cambridge.
That graph makes me sad
"First they came for the slanderers and i said nothing."
It would still be extremely relevant, since not all compute problems are sequential in nature. For example, I may want to repaint my screen at the same time as I calculate the values required rather than calculating all the values first and then finally starting the repaint. 5 truly parallel processes at 1hz is five times as efficient, just as 5 truly parallel processes at 500 Ghz is 5 times more efficient. If history has taught anything with computers it is that we are far from having more computing power than we can find a use for.
Guns don't kill people; Physics kills people! - John Lithgow as Dick Solomon on Third Rock From The Sun
A LONG time. Graphene is not even close to prime time yet. It leaks current like a colander leaks water and has such low gain (current or voltage take your pick) to make it nearly useless as a switch. Graphene *might* find use in broadband RF amps at lower power, but it's going to waste huge amounts of energy and you won't get much gain in the process. I'm not sure what value it will be, even in that application.
They are going to have to come up with some modifications to the graphene crystal structure to make it not leak current and leave the desirable characteristics in place before this is going to be viable in digital devices. Given the materials engineers have been going after this for decades and have not yet come up with a solutions, I'm not holding out much hope for an easy solution.
Silicon is indeed unique, in it's character and location on the Periodic Table. We will be hard pressed to come up with something that is as usable in digital electronics to replace silicon. We might be able to engineer a material that is useful and graphene does have promising aspects. but it's a long way from "shows promise" to "you can buy it".
"File to fit, pound to insert, paint to match" - Aircraft Maintenance 101
Of course, 1,000 GHz should be fast enough for anyone...
NAND? Don't leave us hanging.
(-1: Post disagrees with my already-settled worldview) is not a valid mod option.
Does anyone else remember this same kind of thing being said about Tunnel Diodes several decades ago? There were very few things actually sold with Tunnel Diodes in them. The only one I have is a very old Heathkit dip meter which never did work very well. Negative Resistance devices seem to keep popping up from time to time, but they also seem to be very difficult to get to work in a real circuit.
Why couldn't they make an x86-64 compatible CPU using this (or in fact, any other) CPU technology?
Perhaps the first few CPU's will be custom a ISA, but after they learn how to build full CPU's with this technology, there is nothing stopping them from making ARM or x86-64 compatible CPU's.
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Silicon transistors with sub picosecond switching times were fabricated in 2002. That's in the THz range.
What holds back processors today is mostly the RC delay of metal wires.
FYI, here's the full post where the graph came from.
We hope your rules and wisdom choke you / Now we are one in everlasting peace
However we got more Cores. So there is more parallel processing going on.
Bad if you are still using DOS, but we learned to open up a bunch of apps without worrying anymore.
If something is so important that you feel the need to post it on the internet... It probably isn't that important.
Even if it is a custom ISA, at 400GHz I'm pretty sure it can just emulate any existing CPU without even breaking a sweat.
A little-known example of negative differential resistance is the common electric arc. In an arc, as the current increases the arc gets "fatter" (wider), and so the voltage across the arc decreases. Increasing current with decreasing voltage is negative differential resistance. This enables oscillations, which were first encountered as audio noise in electric arc lighting in the mid-1800s. These led to William Duddell's "Singing Arc", in which Duddell added a tuned circuit to the negative resistance, creating a stable audio tone. The next step was obvious; he wired a keyboard to the arc and made the first electronic music.
Danish physicist Valdemar Poulsen took Duddell's audio oscillator and, by placing the arc in a transverse magnetic field, and in a hydrogen atmosphere (and somehow not getting blown up in the process), moved the frequency of oscillation up into the low radio range, around 500 kHz or so. This was the arc radio transmitter. It differed from the more common spark transmitter in that the arc's output oscillation was continuous, while that of the spark transmitter was a damped (decaying) oscillation.
The arc transmitter caught the attention of Cyril Elwell, of Palo Alto, California, who arranged to obtain the rights to the arc from Poulsen, and started commercial production of it with his company, the Federal Telegraph Company. The arc transmitter became a big success in World War One, when transmitters as large as 1 MW (one million watts) output were installed by 1918.
Much as the Fairchild Semiconductor Company spawned several successful companies in Silicon Valley in the 1960s, Federal did so, too, 50 years earlier; refugees from Federal formed well-known companies like Magnavox and Litton Industries.
Your graphene question has been addressed by bobbied, and the answer to your other question is: right now. Modern GPUs can produce constant 60+FPS on crysis 1 at full details quite easily. In fact, they can do that for crysis 3 (think nvidia titans in sli). It'll just cost you quite a lot. But it's already doable.
The next stage is going to be 4k rendering, and for that, we're not quite at 60FPS+ yet. Though there we are not only hitting the output of modern GPUs, but even the GPUmonitor interface starts to be pushed to the limits.
That wasn't the only part of the summary that was wrong; about the only part that was correct was the part that stated that they were able to perform an XOR in graphene with 3 FETs due to negative differential resistance.
that's what's great about bandgaps in silicon. The electron doesn't travel, it teleports.
they solved that in 2012. Do try to keep up.
The Kruger Dunning explains most post on
And they'll a a linux distro in a week.
And Apple will change their architecture 2 years later.
The Kruger Dunning explains most post on
The focus shifted from more MHZ to doing more with them. Mostly parallelisation, more specialised hardware abilities and more efficient pipelining.
Still sucks for those algorithms that can't be made parallel, though.
Hey, DOS was awesome. You could concentrate well on one thing at a time and get stuff done. Hardware-accelerated text console at your fingertips. Direct fast hardware access. Very fast startup.
...they want their joke back.
systemd is Roko's Basilisk.
...they want their 1990s back.
CLI paste? paste.pr0.tips!
Mainly because more MHZ proved to be impossible, but the space was there on the chip, so why not add an extra core if you can't do anything else? A doubled MHZ is better than an added core.
"First they came for the slanderers and i said nothing."
The 1990s were a joke.
This sig is not paradoxical or ironic.
The GHz war didn't end it just got to the point where pursuing higher clock speeds caused performance due to other architectural constraints. So the focus became on getting more efficient on every clock cycle which we did and then we hit a wall there too.
Now the focus is on paralleling tasks but guess what, now we're hitting a wall as to how to make effective use of those cores, and some of us wish the GHz war would be back so we can get some faster clock speeds again.
Not really. They have some improvements to the current leakage issue, but we are not quite there yet.
From my understanding (and that is admittedly somewhat limited, not being active in research on this) the state of research is that they can build working logic with graphene, but that they still require huge amounts of current and dissipate huge amounts of heat compared to the current silicon designs. The issue is the uncontrolled current leakage and a woefully low gain of a graphene transistor. I suspect that their "working logic gates" require huge amounts of real estate and can only be operated for very short periods before they get too hot.
it's going to be awhile yet...
"File to fit, pound to insert, paint to match" - Aircraft Maintenance 101