

I.B.M. Reports Nanotube Chip Breakthrough - sew
http://bits.blogs.nytimes.com/2012/10/28/i-b-m-reports-nanotube-chip-breakthrough/?hp&pagewanted=all

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abtinf
Articles like this used to excite me. But now, they are just sort of
depressing.

Would it be good to have denser transistor counts? Sure. There are lots of
benefits for hardware. Denser transistors can mean (possibly) reduced power
consumption from smaller chips. Manufacturing costs are reduced because you
get more chips from the same materials. Device production costs are reduced
because you can combine functions that used to take two chips into a single
chip. Overall devices can be smaller.

But from a software perspective, its a limited blessing. To be sure, there are
benefits for cloud computing applications and other "embarrassingly parallel"
applications. These chips might be great in data centers, which are power
sensitive. And being able to do more things at once can be good, even if its
at the same speed - Google can maybe crawl the web more frequently and video
games might get improved graphics.

But the thing is, we already have nearly unlimited computing power at our
disposal. On a whim, I could spin up a hundred thousand computers on Amazon
Web Services to do some desired computation (which would cost a mere $700/hr
at the current spot prices). My laptop has a 192 core GPU which, by itself, is
more powerful than most super computers that existed up to the mid-1990s.

What we really need are software advances to exploit this hardware. For
decades, there has been essentially no progress whatever in software that can
take advantage of parallel computing. What techniques we have are either
brittle (threads) or forfeit most of the hardware's power (multiple processes
combined with relatively slow inter-process communication). Software is in
such a backward state that people are amazed when the home-screen icons on an
iphone scroll smoothly from page to page.

~~~
Symmetry
The density numbers in the article are only interesting because they mean that
nanotube transistors are practical. A 90nm process node is what we were using
for Athalon 64s and Pentium 4s, it won't let you put more cores on a chip than
you have now. Maybe someday nanotubes will shrink that small, but that wasn't
what the article was about.

The amazing thing about nanotubes is that they have an electron mobility of
100,000 cm2/(V·s) at room temperature, the highest of anything you could think
about making a transistor out of. By contrast, silicon has an electron
mobility of only 1400 cm2/ (V·s). Since the drive current coming out of
transistor is roughly proportional to electron mobilty (or equally high hole
mobility) you'd expect that you'd expect that a nanotube based transistor
would be able to switch 70 times as fast as a silicon based one. Or a quarter
of a terrahertz, in other words. Now, speed of light delays at 90nm will
probably be pretty significant at that point, but we should still expect that
moving to nanotubes to be a huge win for single threaded performance at the
expense of the number of threads available.

~~~
Tuna-Fish
> ... a nanotube based transistor would be able to switch 70 times as fast as
> a silicon based one. Or a quarter of a terrahertz, in other words.

A transistor switching at 250GHz would _not_ be 70 times faster than a silicon
transistor. In fact, it would only be a little over 2x faster. Our best
production quality silicon transistors are well over 100GHz now.

The clock frequency of a CPU is _not_ the speed that a single transistor in
that CPU switches. It's the speed that the longest path of transistors inside
a single pipeline stage in that CPU switches. In contemporary CPUs, these
paths are ~20 FO4¹ long.

(¹ since the speed of the transistors depend on the load put on them, you need
to normalize for that. <http://en.wikipedia.org/wiki/FO4> )

~~~
Symmetry
You're entirely right that I misspoke there. I meant that the _clockspeed_ for
similarly architectured devices would go up to a quarter terrahertz, but I
managed to imply something entirely different.

~~~
Tuna-Fish
No, it really wouldn't. Clock speed is as much restricted by light speed
delays as it is by transistor switching speed.

~~~
Symmetry
Ok, I'm going to disagree with you here. Speed of light delays cause latency
when you're talking about large structures like caches, but they're not even
the biggest factor in L3 with current processes. If we were clocking things as
fast as nanotubes allow then we probably would find speed of light delays
dominating latencies, but increased latencies will only eat a proportion of
the gains from higher clock speed, and that's what we have branch predictors,
prefetchers, and deep OoO engines for.

Unless you were talking about clock skew between the exit points of your
h-tree?

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tisme
IBM is fantastic at using their research for PR, but it usually takes a very
long time until these breakthrough announcements show up in products. The
challenges on the road to competing with established tech for a completely new
technology like this are formidable.

An announcement like this is great but it is no reason to get overly excited
just yet. Many other technologies have been proposed and have either
disappeared or have found employment in niches (GaAs for instance), for now
Silicium still holds a formidable edge when it comes to the most important
measure of all: economy.

~~~
devindotcom
This particular breakthrough product probably wouldn't start appearing in
chips for at least 8 or 10 years, though. It's fine to get excited! Just don't
think we're getting nanotubes in our phones next year. Changing materials is a
huuuge step.

~~~
Symmetry
Right. I expect people to switch over to other materials only after
improvements using silicon stop.

~~~
tisme
Even then it will have to make economic sense to switch. After all the
equation is not x > y but $n using tech x buys more computing power than $n
using tech y.

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hotpockets
article link
[http://www.nature.com/nnano/journal/vaop/ncurrent/abs/nnano....](http://www.nature.com/nnano/journal/vaop/ncurrent/abs/nnano.2012.189.html)

also more informative stories
[http://news.cnet.com/8301-11386_3-57541381-76/ibm-brings-
car...](http://news.cnet.com/8301-11386_3-57541381-76/ibm-brings-carbon-
nanotube-based-computers-a-step-closer/)

<http://www.nanowerk.com/news2/newsid=27115.php>

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mukaiji
material scientist here. I've worked on carbon nanotubes (cnt if you want to
sound cool) for a few years. Looking at them under the electron microscope,
I've always wondered how in the hell we'd ever line them up without having to
recourse to nano-tweezers (which of course is impractical if you want to scale
to a few billion switches). Looks like IBM finally cracked a decent technique
(though I suppose the device yield isn't that great), and it hopefully will be
a path toward production. What would be really cool is if we can find
economically-viable application for carbon nanotubes outside of semi-
conductors. The biggest problem right now is their cost (~$400/gram for good
purity [for reference: 20X the price of gold]) and the fact that platinum is
used as a destructive catalyst to make them.

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carlob
Let me be nitpicky: the price of gold has gone up recently, it's now over
50$/g.

[http://www.wolframalpha.com/input/?i=%28400+%24%2Fg%29+%2F%2...](http://www.wolframalpha.com/input/?i=%28400+%24%2Fg%29+%2F%28price+of+gold%29)

~~~
mukaiji
Ah, good catch! I remember a while back comparing CNT prices per gram versus
gold and it was something like $20 a gram for gold. Must have been a low then.
Thanks for catching it.

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nine_k
TL;DR: IBM found a way to place nanotubes on silicon chips with some
precision. Not yet perfect, but it's the best we got so far.

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megaman821
Any know what the theoretical frequency of CPU made of nanotubes would be?

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btilly
The article claims that the transistors were 5x faster than existing
transistors. And that is not the top possible performance.

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Yuioup
If this ever turns into a product, I hope they choose a more efficient design
than x64. I'm assuming that ARM would be a good choice.

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vrotaru
They have they Power series of chips so it would be really weird if they were
to choose x86 (even x86_64)

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richardburton
It looks like Warren Buffett's first major investment in a technology company
is shaping up nicely.

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stickfigure
_They have long since shrunk the switches to less than a wavelength of light_

Snort.

~~~
wtallis
What? Transistor sizes hit UV wavelengths around 1995, during the Pentium era.
That's a reasonable statement to be making to provide context.

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jamesaguilar
And there are constructive ways to provide that context, like how you did.
"Snort" does not qualify.

~~~
frozenport
I think "snort" was a joke so that you wouldn't get angry :-)

