
MIT Graphene Multiplier May Push CPUs to 1,000 GHz - vaksel
http://www.insidetech.com/news/articles/4375-mit-graphene-multiplier-may-push-cpus-to-1000-ghz
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jerf
Reading the article, it sounded an awful lot like this means we can have
timing signals that run at 1000GHz. This doesn't mean anything at all about
our ability to have other components actually running at that speed.

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yan
Just throwing it out there, light (potential, or any signal) can travel about
0.3mm in one picosecond, which is a clock cycle if you're operating at 1THz.

I don't know how tiny these cores will be, but based on my back-of-the-
envelope calculations, it doesn't sound like it'll be too realistic if we're
talking about CPU cores operating that quick.

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Xichekolas
Well, assuming a current cpu core is ~30mm square, you would need to shrink
the feature size by two orders of magnitude... so current 45nm features would
need to shrink to ~500 picometers.

According to wikipedia, a 'standard atom' is between 60 and 600 picometers in
diameter, so yeah, you'd need transistors the size of atoms.

Of course, this is assuming the same general processor design. You could go 3D
and get everything closer together without shrinking transistors as much... or
you could change the design all together.

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Retric
That's one option the other is using a longer pipeline.

However, the cache does not need to operate at that speed only the core so
it's best to ignore the cache, but I can't find good numbers on a naked CPU.
Anyway, using a 55nm GPU 285 GTX that has a 470 mm die size and 240 processor
elements we can see each element is only using ~2mm of die. Which is only off
by a factor of 4 so ~14nm would work.

In theory you could end up with a ~1THz GPU with ~1000 SPs and around 4000x
more processing power. But it would need insane memory bandwidth etc.

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ComputerGuru
Longer pipelines proved to be pretty much a dead end with the Pentium 4.

They're great and all when it comes to benchmarks and stuff, but their design
has a number of serious drawbacks:

1) The control lines for a long pipeline are incredibly convoluted/complicated
as necessitated by the movement of individual instructions from one stage to
the other along the pipeline across many, many cycles (all of which involve
storing the results of the current cycle to a register somewhere along the
pipeline, adding immense overhead in today's systems).

2) Flushing longer pipelines is an incredibly taxing procedure. You either
flush the entire pipeline and lose a huge chunk of work, basically throwing
out several thousand cycles of work as a result of a single branch or value
mis-prediction; or you can selectively clear the pipeline which is an
extraordinarily difficult feat that involves keeping track of which operation
in what order wrote back what data to which register... for dozens of
operations.

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Retric
All modern PC CPU's have a pipeline.

Granted long pipelines suck, but my point was you can have a higher clock
speed than the time it takes light to travel from one end of you're CPU to the
other and back. One of the more interesting options IMO is to have 2 separate
threads with separate registers using the same hardware so you can interleave
calculations without a long pipeline. The issue becomes do you have 2 half
speed virtual cores or a single high clock speed core and what do you do about
instructions that take more than one clock cycle.

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ComputerGuru
Oh, I'm not denying the merits of pipelining - no one can. I'm just saying
that nothing is good when taken to the extreme.

The "more interesting option" you're referring to is implemented in P4 and
Nehalem under the trademark of "HyperThreading."

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scott_s
The non-marketing name is Simultaneous Multithreading (SMT), but I've never
been impressed with SMT performance. I think the emerging processors that use
many simpler cores will have more impact.

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blackguardx
It is just a clock multiplier. Generating high clock frequencies was never the
biggest bottleneck to faster CPU speeds.

They are spinning their research to be more mainstream. This probably has
better application to THz communication and imaging applications like those
airport scanners that can see through clothing. Currently, they generate the
THz signals using lasers.

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habibur
Modern processors already run 250 times faster than the memory system is able
to feed data into it. Caches can't help to cover this lag much. I wonder how
that machine might run things faster than what current processors are doing
unless this memory speed problem is fixed.

By the way, human brain works at 10 Hz only (not even KHz) and can still
process information faster than all these CPUs.

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MikeCapone
the information I have about the human brain is that neurons works at about
200hz (there is variability).

It's not faster than CPUs in many things, but where it is, it wins because it
is massively parallel (so that helps for pattern recognition, but not to solve
difficult linear equations).

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lsb
I'm sitting in on Marvin Minsky's Society of Mind class, and he keeps
reminding us that MASSIVE PARALLELISM IS NOT THE INTERESTING ASPECT OF THE
MIND.

Think about playing chess. Each move, there's 30 branches to follow. If you
have a million machines, you can evaluate about 2 moves ahead before
parallelism runs out. If you have bad branch prediction, you'll follow all the
wrong paths.

Humans beat machines at creative endeavors because computers don't know what
branches to follow. There was nothing interesting about the implementation of
Deep Blue. It would be like implementing the Internet by shipping immense hard
drives around to convey information: brute force, unintelligent, and immensely
successful at delivering throughput.

We process information much slower than CPUs (how fast can _you_ read
Wikipedia?), but we know when to give up, we know when to follow an
interesting path, we know how to move processing to the subconscious.

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sown
Biology is very much a show-me science and I've always wondered about Society
of Mind ... what's his proof?

I mean seriously, is it all just reasoned out? Is it like philosophy?

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Drewcifus
Ya know what, I dunno why you guys are all philosophising about all this
stuff, as opposed to just having it BUILT ALREADY. I mean really, what does it
take? So you take the ATX motherboard design, and scrap it. It's crazy old
anyways. And if you can grow, or create graphene in a controlled environment,
WHY does the graphene have to be a "CPU only" material? Why not use it for
RAM, GPUs, and Cache??? I mean really. And this is what I want to know...
WHERE is Intel in all of this. THEY are the major chip-maker of planet earth.
It's not like they don't have the money to build a new architecture for
graphene. It's not like they can't build a proper fabrication plant. So WHY
isn't MIT working with Intel on this one...? Duh.

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aidenn0
This seems entirely uninteresting for CPUs since there are all sorts of issues
with regard to that. However, THz frequency signals have all sorts of other
uses (<http://en.wikipedia.org/wiki/Terahertz_radiation>)

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Hexstream
I'm thinking, even if we had infinitely fast CPUs, we might not gain so much
because it would just reveal other bottlenecks. Not that I'd mind having an
infinitely fast CPU...

