
How low (power) can you go? - cstross
http://www.antipope.org/charlie/blog-static/2012/08/how-low-power-can-you-go.html
======
yaakov34
A couple of notes about the limits of things that have already been reached
today:

A pixel in a camera sensor has to be a couple of wavelengths in size. This is
basically the size that we can make them now. There are also diffraction
limits for any imaging system, and a size limit on the lens (if your lens is
too small, its surface won't collect enough photons in low light to make an
image - no matter how you focus them). So I don't think it would be possible
to make a deep sub-millimeter camera with usable image quality, and I don't
think the 10-order-of-magnitude gains in power efficiency will be coming,
either (if you can't shrink it, you're stuck switching larger circuitry and
dealing with larger charges). Now, spy cameras can already be annoyingly tiny,
but I don't think we're headed for cameras on a speck of dust or some such.
One piece of evidence for this is that tiny sub-millimeter insects have lost
most or all of their vision - eyes don't scale well to these sizes.

Genome sequencing: I think there are limitations to what can be done with
these that are already being hit. E.g. looking at the USB-attached genome
reader that Charlie Stross mentions, I see that it really needs to have the
material which you're feeding it to be separated into DNA/non-DNA fractions
for decent performance (otherwise, the micropores will be deluged by non-DNA
material), and it needs a conventional chemistry lab in order to cut something
as large as a human genome into manageable chunks. For this you need things
like centrifuges, which can't become microscopic. I think there are
fundamental limits reached here as well, since you can't make a pore
arbitrarily small (molecular-sized) without having all sorts of molecular junk
jam into it, if it is present.

~~~
ericb
Theoretically, a single pixel camera that scanned fast enough and held the
result in memory could create an image with many pixels, so it seems like this
barrier isn't necessarily absolute.

~~~
stcredzero
But how well is that going to work in dim light? You're going to hit a limit
to how fast you can scan given the time it takes to gather enough photons.
When you start to have to be too clever is when you've started to hit limits.

~~~
StavrosK
That's about two decades ago, then.

~~~
stcredzero
None of that was too clever, obviously.

------
lsiebert
Either processors could share cameras, or each processor could have a low
resolution camera that works in aggregate, perhaps similar to how a fly's eyes
work. Or we could have both. Computer vision doesn't have to replicate human
vision to be useful, especially if the processing is fast enough.

------
ctdonath
I've occasionally mulled what a 1-bit camera could do, in the same notion as a
1-bit audio A/DC. Cross this with CS's gazillion millimeter computers and
emerging 3D image extraction (term escapes me, take lots of photos and deduce
the source objects a la Google 3D Maps).

One camera may be too small for an image (both resolution & color depth). A
lot of them, thrown randomly around, may provide interesting results given
enough math.

~~~
eru
See <http://dsp.rice.edu/cscamera> for an almost practical single pixel
camera.

------
eru
Nobody mentioned that Moore's first law isn't just about the number of
transistors doubling. It's about the number in the chip that's cheaper per
transistor.

Also there's Moore's second law about the cost of fabs rising exponentially at
about the same rate. If GDP growth doesn't accelerate dramatically, we won't
be able to afford fabs any longer in a few decades.

------
codedivine
I think the assumption that Moore's law, or even Koomey's law, is going to
hold for another two decades is wildly optimistic. I would expect a taper off
much sooner, perhaps even this decade.

The physics and the economics of smaller process nodes is becoming harder and
harder, to the point where anything beyond 10nm or so looks extremely
difficult.

~~~
eleitl
Indeed, see [http://www.semiwiki.com/forum/content/1388-scariest-
graph-i-...](http://www.semiwiki.com/forum/content/1388-scariest-graph-i-ve-
seen-recently.html)

~~~
Someone
That graph ignores that there will be pressure to go to smaller sizes not to
get more power for the same size, but to get the same power for less power
usage.

On the other hand, I would like to see a graph plotting time or nanometers vs
cost of the factory needed to make them. I cannot find one, but I remember
seeing ones that hinted that the cost of making a production line would become
prohibitive for everyone.

------
wwalker3
Stross' comparison between Cray 1 performance and that of a modern smartphone
seems off. He says: "A regular ARM-powered smartphone, such as an iPhone 4S,
is some 12-13 orders of magnitude more powerful as a computing device than a
late 1970s-vintage Cray 1 supercomputer."

A Cray 1 could peak at about 250 MFLOPs/s
(<http://en.wikipedia.org/wiki/Cray-1>), and a modern smart phone like the
Galaxy Nexus peaks at about 9.6 GFLOPs/s (using ARM Neon instructions on both
cores). That's less than two orders of magnitude difference.

Floating-point power efficiency seems to have improved by about 6-7 orders of
magnitude in that time though, which is very nice :)

~~~
lmm
Maybe he's comparing integer operations? ARM has relatively underpowered
floating-point because most of the uses for an ARM (at least historically)
don't involve it.

~~~
maxerickson
He notes it is a mistake in the comments.

But the details of the comparison don't change the part where a modern cell
phone is nicely comparable to a $millions computer from a few decades ago.

------
eleitl
Apparently, Charlie hasn't gotten the memo:
[http://www.semiwiki.com/forum/content/1388-scariest-
graph-i-...](http://www.semiwiki.com/forum/content/1388-scariest-graph-i-ve-
seen-recently.html)

These are financial limits, the scaling limits will end at about 1-3 nm. But
it will take longer, as doubling will no longer in constant time.

~~~
Symmetry
Well, that does imply that we could keep making the same processors at smaller
sizes for the same price. Power density issues might constrain speeding things
up at that point, but it would certainly be a continuation of Koomey's law.

EDIT: Maybe more likely is that we might be seeing a future slowdown of
Moore's law to a doubling every 24 months or more, allowing fabs more time to
amortize their investments. This would be bad, but not the end of the world.

------
pressurefree
fluorescent LEDs

