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>> "[T]here is a limitation to how small, fast and compact silicon computer
>> chips can be. DNA computers show promise because they do not have the
>> limitations of silicon-based chips."
>>
>> O RLY?
>
> Of course there's a limit. And there's likely a limit on how small/fast
> a DNA-based machine could be as well.
In reality, the nature of matter (and quite possibly time and space
itself) is quantum. Therefore *every* technology has limits.
Now a DNA computer could potentially be very much smaller than current
silicon ones. This is not the same statement as "DNA computers do not
have the limitations of silicon-based chips".
>> "Secondly, the DNA chip manufacture does not produce toxic by-products."
>>
>> Riiight. So because the end product is DNA, a molecule that already
>> exists in nature, therefore you can produce it with no toxic by-products?
>>
>> And the DNA itself wouldn't be toxic, no?
>
> Not unless it codes for something that could cause illness or kill you,
> but who's paying attention anyway.
A virus is nothing more than a stand of DNA or RNA (in some cases coated
with proteins, but not always). Now, it's highly unlikely that the DNA
sequence used by a computer would /just happen/ to code for viral
activity within human cells. It's /completely plausible/ though that if
some of that stuff gets inside you, it will make the cells it enters
synthesize endless amounts of some useless protein until they
prematurely die as a result.
A chemical that kills living cells it touches? Yeah, I'd call that
pretty toxic. (Still, you presumably don't need to make that much of it...)
> Organic compounds are some of the
> most toxic to us, because they are the most likely to interact. To be
> sure, there are a lot of extremely toxic inorganics as well.
To be sure, there are lots of organic compounds which are "designed" to
be toxic to us. But even ones that aren't sometimes end up
"accidentally" being toxic. (E.g., the black widow's venom isn't
supposed to kill mammals, it's meant to kill insects. And, indeed, it's
completely harmless to cats and dogs - yet just happens to be lethal to
humans...)
>> "Last but not the least, DNA computers will be much smaller than
>> silicon-based computers as one pound of DNA chips can hold all the
>> information stored in all the computers in the world."
>
> Storage is not the same as computation.
Agreed.
> No mention as to how fragile that pound of DNA is.
Also agreed, since DNA is very, very definitely biodegradable. (In fact,
human skin is coated in enzymes designed to snip up RNA, as a protection
against viruses composed of RNA...)
>> Current computers are much, much larger than strictly necessary mainly
>> due to issues of heat dissipation. You can already make RAM chips that
>> hold absurd quantities of information; it's just that they tend to melt
>> when you switch them on.
>
> I believe the bigger limitation on the amount of information that RAM
> can ultimately hold is more about the lower limit on the size of a
> transistor, rather than heat.
I still suspect that if you weren't worried about heat, you could
"stack" layers of silicon on top of each other, producing 3D circuitry
which takes up a fraction of the space.
>> "The capacity to perform parallel calculations, much more trillions of
>> parallel calculations, is something silicon-based computers are not able
>> to do."
>>
>> I beg to differ.
>
> You'd need the pipelines to do it in the chip die. You'd need to build
> very small computational units to get that massively parallel.
True. But, as I understand it, transistors are /already/ "very small".
The reason that people like Intel and AMD build chips containing several
thousand million transistors which only comprise two or three "cores" is
because nobody has really figured out how to make use of lots of cores.
(Let's face it, Cray have been making vector machines for decades...)
> I don't get how DNA can compute anything. DNA is essentially a coding
> for proteins. What would your end result of a computation be? A glob of
> proteins that mean some sort of result?
If you read some website which actually *explains*, in technical detail,
what a DNA computer is, you will discover that the DNA is just the
storage medium. Essentially the DNA is your RAM, and enzymes are your
computational hardware. So some DNA goes in with the input data encoded
on it, and new DNA comes out with the result coded on it. (Wikipedia
indicates that the enzymes function something like an actual Turing
machine, with the DNA as the "tape".)
>> "In the current technology of logic gates, binary codes from the silicon
>> transistors are converted into instructions that can be carried out by
>> the computer."
>>
>> This is a highly questionable and very muddled statement.
>
> The statement doesn't seem to make a lot of sense.
Indeed.
>> "though it may be very fast in providing possible answers, narrowing
>> these answers down still takes days."
>>
>> This rather suggests that the operation of a DNA computer is
>> non-deterministic (and hence, applicable to a much smaller set of
>> problems than a Turing-complete machine).
>
> Huh? Computers can very quickly give exact answers to a wide class of
> problems.
I'm saying that this description implies that DNA computers aren't
Turing-complete.
According to Wikipedia, actually they can be. It's just that each
"computer" is a single molecule, so typically you run millions of them
at once, in parallel. The slow part, presumably, is synthesizing the
reactants, and then analysing the reaction products to get your answer
back afterwards.
> What is needed, really, is more
> improvements on existing algorithms to allow them to operate in parallel
> on simpler computational units. Once a high degree of parallelism is
> met, then we'll see some huge jumps in how fast these silicon machines
> can really work.
I agree.
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"D103" <nomail@nomail> wrote:
>
> This may be of little consolation now, but maybe in 20 years or so...
>
> http://www.tech-faq.com/dna-computer.html
>
> Imagine a computer with a CPU about the size of a coin, capable of 66 Gigaflops
> and having 700 Terabytes internal memory AND a power consumption of ~
> 0.0000000001 watts (minus the screen and interface devices, of course).
>
> That should speed up rendering!
>
> D103
After posting this I realized that most of my info (apart from the link) was 7
years old, and while perhaps not out of date, it was only hypothesis.
Also, I have yet to finish high-school so my knowledge of computers and how they
work is somewhat limited.
D103
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D103 wrote:
> Also, I have yet to finish high-school so my knowledge of computers and how they
> work is somewhat limited.
Back in high school I found in the library a wonderful text. It was a huge
hardback book about 3 or 4 cm thick. It started with vacuum tubes, tube
diodes and triodes, then went into semiconductor tech, including what a
semiconductor *is*, how the doping affects its behavior, how a diode works,
an LED, a transistor, a thermistor, etc. Then into chips, how to make
transistors on a chip, how the doping is done, then gates from that.
I wish so much I remembered what that book is called. It taught me 90% of
what I know about hardware.
After that, the SAM'S book on the 8080 pretty much taught me the basics of
computer architecture, instruction sets, etc.
It's a shame in some ways that everything has gotten so complicated that you
wind up with either a quantum physics textbook or a "Teach Yourself
Microsoft Word in 24 hours" sort of book, and nothing really in between that
I know of.
--
Darren New, San Diego CA, USA (PST)
Serving Suggestion:
"Don't serve this any more. It's awful."
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Darren New <dne### [at] san rrcom> wrote:
> Back in high school I found in the library a wonderful text. It was a huge
> hardback book about 3 or 4 cm thick. It started with vacuum tubes, tube
> diodes and triodes, then went into semiconductor tech, including what a
> semiconductor *is*, how the doping affects its behavior, how a diode works,
> an LED, a transistor, a thermistor, etc. Then into chips, how to make
> transistors on a chip, how the doping is done, then gates from that.
> I wish so much I remembered what that book is called. It taught me 90% of
> what I know about hardware.
> After that, the SAM'S book on the 8080 pretty much taught me the basics of
> computer architecture, instruction sets, etc.
Do you really need to know how a vacuum tube works in order to know how
a modern computer works?
I mean, it may be interesting knowledge in a historical sense, but is
there any practical application to this knowledge? (In computing science,
that is. In guitar amps vacuum tubes are quite popular, although for a
slightly different reason.)
> It's a shame in some ways that everything has gotten so complicated that you
> wind up with either a quantum physics textbook or a "Teach Yourself
> Microsoft Word in 24 hours" sort of book, and nothing really in between that
> I know of.
I'm sure there are in-between books as well.
--
- Warp
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Warp wrote:
> Do you really need to know how a vacuum tube works in order to know how
> a modern computer works?
Well, at the time, TVs still ran on vacuum tubes. I guess with the death of
CRTs, only people running medical equipment care about how they work now.
But that's why it was a 1200-page tome. It went all the way from vacuum
tubes to TTL and CMOS circuits. You could probably drop the first half of
the book and it would still work.
You didn't have to know it, but it might be a little easier to understand
semiconductor transistors if you can make an analogy to vacuum tubes, perhaps.
> I'm sure there are in-between books as well.
College text books, I guess, sure. They're just not common. Do a search on
"computer hardware textbook" and you get "how to use Windows 7" and
"Understaning Access" as the first hits. :-)
http://www.amazon.com/Principles-Computer-Hardware-Alan-Clements/dp/0199273138/ref=sr_1_fkmr0_1
I mean, look at the TOC of this, the first book on amazon for the search of
"computer hardware textbook". Nothing in the TOC obviously about the
semiconductor level. Gates, yes, bits, yes. 100 pages talking about gates,
zero talking about semiconductors.
The "computer architecture" goes from page 205 to 209, followed by 50 pages
about the instruction set. Nothing actually gets all the way down to the
*hardware*. From what I can tell of the TOC, nothing there tells you how
many pins a transistor has, for example. As I go on, I see chapter 7 looks
like it might address some of the same stuff the SAM's book I referred to
addressed. But still no hardware. Actually, other than that, it looks like a
really good textbook. :-)
That said, *this* one sounds pretty good, but without looking into it it's
hard to say:
http://www.amazon.com/Semiconductor-Devices-How-They-Work/dp/041258770X/ref=sr_1_1
I guess everything just got complexer, to the point where it doesn't make
sense to put it all in one book.
--
Darren New, San Diego CA, USA (PST)
Serving Suggestion:
"Don't serve this any more. It's awful."
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>
http://www.amazon.com/Principles-Computer-Hardware-Alan-Clements/dp/0199273138/ref=sr_1_fkmr0_1
>
> I mean, look at the TOC of this, the first book on amazon for the search
> of "computer hardware textbook". Nothing in the TOC obviously about the
> semiconductor level. Gates, yes, bits, yes. 100 pages talking about gates,
> zero talking about semiconductors.
Maybe because this area is more covered by electronics textbooks? In my
courses everything from electrons up to simple logic circuits like
bistables, adders, counters etc were handled in the "electronics" courses.
The "computing" courses started off assuming you knew what logic gates did -
even if you couldn't remember exactly how they did it or how to wire one
up...
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scott wrote:
> Maybe because this area is more covered by electronics textbooks?
It's entirely possible I'm looking at the wrwong search terms. :-)
--
Darren New, San Diego CA, USA (PST)
Serving Suggestion:
"Don't serve this any more. It's awful."
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