9 ms·

"Unlike transistors, neurons are intrinsically rhythmic to various degrees due to their ion channel complements that govern firing and refractory/recovery times

"Unlike transistors, neurons are intrinsically rhythmic to various degrees due to their ion channel complements that govern firing and refractory/recovery times. So external "clocking" is not always needed to make them run." Transistors don't need a clock in order to run. They can in fact be set up to create their own clocks. The purpose of clocks is for synchronization across the chip so that we mere mortals can modularize the operation of a CPU. That is, clocks exist mostly so that we can think in terms of sequential gate operations (or from the programmer point of view, assembly code). The author seems to confuse the chosen approach to designing computers (VLSI), and the actual physical capabilities of a transistor. We have opted over the last forty years to develop the CMOS logic gate way of organizing computers. There are other ways, as the brain demonstrates, but it is not clear at all that you can't do it with novel transistor topologies.

brudgers 15y ago
Whenever I see comparisons of the brain to a computer along with the implicit suggestion that computers will someday replicate brains, I am reminded of this passage from Leibniz's Monadology and that today's computers are but yesterday's mills: "Moreover, it must be confessed that perception and that which depends upon it are inexplicable on mechanical grounds, that is to say, by means of figures and motions. And supposing there were a machine, so constructed as to think, feel, and have perception, it might be conceived as increased in size, while keeping the same proportions, so that one might go into it as into a mill. That being so, we should, on examining its interior, find only parts which work one upon another, and never anything by which to explain a perception. Thus it is in a simple substance, and not in a compound or in a machine, that perception must be sought for. Further, nothing but this (namely, perceptions and their changes) can be found in a simple substance. It is also in this alone that all the internal activities of simple substances can consist." [http://philosophy.eserver.org/leibniz-monadology.txt http://philosophy.eserver.org/leibniz-monadology.txt] [http://en.wikipedia.org/wiki/Monadology http://en.wikipedia.org/wiki/Monadology]
- archgoon 15y ago
  Wow. Leibniz constructed the Chinese Room Argument nearly four hundred years before John Searle or computers. Nice. :)
  - hasenj 15y ago
    I constructed it in my head when I was in college. I think lots of people do that; it's not a very complicated idea at all. It's just that some people wrote it down and their writings somehow became famous. When I constructed a similar argument, it was simply an argument I was having in my head with an imaginary person who was arguing with me that computers can have perception just like humans.
  - brudgers 15y ago
    A homunculus is a homunculus, but nevertheless Searle's Chinese Room is perhaps a bit more radical - not so much conceptually but rather because it was proposed in contradiction to a well entrenched belief system - behaviorism.
- deleted 15y ago
  [deleted]
- barrkel 15y ago
  There is an exactly analogous argument about the human brain and its cells; and I understand the Turing test as a thought experiment that shows it to be invalid in any meaningful sense. If a machine (or a seeming person on the end of a terminal) says they perceive and think, how are you to argue otherwise? You have no evidence other humans, let alone other machines, actually can perceive or think, other than how they seem to act.
  - deleted 15y ago
    [deleted]
  - brudgers 15y ago
    IMO, the Turing test is conclusive to the extent one accepts Berkleyian idealism and abandons a belief in the necessity of other minds. Under those premises, solutions to the Turing test are, at this point, trivial as ELIZA long ago demonstrated. http://en.wikipedia.org/wiki/ELIZA http://en.wikipedia.org/wiki/ELIZA
    - translocation 15y ago
      I would argue that ELIZA, and the chatbots that have been programmed since, are not solutions to the Turing test. Have you ever tried holding an actual conversation with a chatbot? They almost invariably fail the real-life Turing test within two or three messages. They parse natural language incorrectly, they can't keep track of the topic of conversation, and they often reply with non-sequitor errors. Certainly, chatbots can appear to act with intelligence in certain situations. Given enough back-and-forth communication, however, a human will always realize that the bot is just parroting words and phrases that are statistically relevant to the human's questions. I don't think it's unreasonable to define Turing test success as the ability to consistently fool ordinary human beings through intelligent communication- and that, so far, has not been accomplished.
      - brudgers 15y ago
        >"Given enough back-and-forth communication, however, a human will always realize that the bot is just parroting words and phrases that are statistically relevant to the human's questions." That however is not the Turing Test at all. Here is what Turing actually wrote: I believe that in about fty years' time it will be possible, to programme computers, with a storage capacity of about 109, to make them play the imitation game so well that an average interrogator will not have more than 70 per cent chance of making the right identication after ve minutes of questioning. http://orium.homelinux.org/paper/turingai.pdf http://orium.homelinux.org/paper/turingai.pdf
- adrianN 15y ago
  "Thus it is in a simple substance, and not in a compound or in a machine, that perception must be sought for" This is an incorrect conclusion. You can inspect individual grains of sand as long as you want, you will never find a beach. Yet beaches are composed of sand with no magic involved.
  - brudgers 15y ago
    On the other hand a beach also is part of a shoreline, and thus you will not find a beach at Great Sand Dunes National Park http://en.wikipedia.org/wiki/Great_Sand_Dunes_National_Park_and_Preserve http://en.wikipedia.org/wiki/Great_Sand_Dunes_National_Park_...
    - ugh 15y ago
      What’s your point?
      - brudgers 15y ago
        By "beach" we don't mean "many grains of sand." The parent analogy using grains does no more gets us a beach than using gears and pulleys or RAM and CPU's gets us a brain.
        ugh 15y ago
        We mean many grains of sand in a certain configuration which are also in close proximity to many molecules of water in a certain configuration†. Do you really argue that beaches have some sort of, well, “magic”, I guess, property which makes them a beach? That seems entirely unnecessary for something as simple as beaches. You can map all the grains of sand, you can map all the molecules of water and confidently identify when something is a beach. We know how to explain beaches in terms of grains of sands and molecules of water. We cannot yet explain all properties of brains (most notably consciousness) in terms of, say, neurons but just because we cannot yet doesn’t mean we never will. †What those configurations are depends entirely on your definition of “beach”. Sand or water might also no play a role at all, again, depending on your definition.
- jodrellblank 15y ago
  I put a disparaging remark here, but I really shouldn't insult Leibniz based on one partial quote. More politely, I think it wrong to say "compound substances cannot be perceptive therefore humans have supernatural souls". Brains and bodies are compound substances and have perception. The next step is "I don't understand how" not "tada, souls!".
- ugh 15y ago
  Moreover, it must be confessed that perception and that which depends upon it are inexplicable on mechanical grounds, that is to say, by means of figures and motions. And supposing there were a machine, so constructed as to think, feel, and have perception, it might be conceived as increased in size, while keeping the same proportions, so that one might go into it as into a mill. That being so, we should, on examining its interior, find only parts which work one upon another, and never anything by which to explain a perception. That seems like too big of a leap. Why can't "parts which work one upon another" not create perception? Is this assumption justified? (I really hope the justification is not "because mills that perceive are self-evidently absurd". If it is then my next question is: Why?) If that assumption doesn't stand the rest of the argument falls flat. I would like to hear a bit more about why compound parts can't create perception. The brain certainly looks like it consists of compound parts. We obviously cannot (yet) explain consciousness so it is possible that it is impossible to create consciousness with compound parts, we just don't know. In that light Leibniz's argument seems unconvincing, at least as far as I can understand it.
  - ryanklee 15y ago
    I believe that parent's point is precisely that it is indeed unconvincing and so we should in turn be mindful that our own idea that the brain is a computer will, it is possible, given further technological advances, come to strike us as just as unconvincing as Leibniz' argument. Metaphors of the brain follow along with the state of the arts of technologies. For the ancient Greeks, the human composition (they didn't talk yet of brains and consciousness) was the city-state; for early modern natural philosophers, the mill and the like; during the industrial revolution, machines; and now, with us, computers and computation. It is unlikely that our current analogy is any more or less true than previous ones, that is to say, they may be illuminating in some way and not entirely useless in our thinking about brains and consciousness, but as it goes, they are not and cannot be true because the conjectures cannot even in the end be shown to be wrong. Consciousness and the brain may not be in the end inexplicable, but I very much doubt that we will find that the brain and consciousness are something else other than the brain and consciousness, like, for instance, a mill or a computer. It would be the most surprising thing of all were we to find out that evolution produced a kind of technology before in fact that technology as a human tool was ever produced -- but that is a different argument and I'm not even sure what I mean by it.
- lolcraft 15y ago
  Leibniz was an idealist. He lived in peculiar ideological waters: he was Christian. He had to believe that there's the mind, there's reality, and both never touch. If he ever went out the party line, the inquisition would take care of him. According to Leibniz, neurons can't exist. Exercise does not improve your mood. Brain surgery is useless. Caffeine does not work. Hormones do nothing. Coma is unexplainable by definition. And so on. Reality killed Leibniz.
  - lists 15y ago
    Actually the theory of monads bypasses the mind/body dualism by asserting a kind of synchrony. Spinoza made the same move in a different way by claiming God is the multi-dimensional plane of existence whose varying realms (mind and extension [body] being just two of an infinite number) are completely synchronousness. You're also off with the Christian comment since Leibniz wasn't within the domain of the Catholic church.
  - michaeldhopkins 15y ago
    St. Luke understood the brain to be the home of mental faculty and the situation never really changed. Especially once Aristotle re-appeared, the brain was definitely understood as an organ that processes sensory input can be affected like other organs. Caffeine, exercise, possibility of surgery all known. Brain speculated to be involved in comas. Existence of neurons speculated.
- ckuehne 15y ago
  Whenever I see Searle's Chinese Room argument, or a version of it, invoked to show that brains cannot possibly be computers I am reminded of a passage of Terry Bison's "They're Made out of Meat" [1]: "They're made out of meat." "Meat?" "Meat. They're made out of meat." "Meat?" "There's no doubt about it. We picked up several from different parts of the planet, took them aboard our recon vessels, and probed them all the way through. They're completely meat." "That's impossible. What about the radio signals? The messages to the stars?" "They use the radio waves to talk, but the signals don't come from them. The signals come from machines." "So who made the machines? That's who we want to contact." "They made the machines. That's what I'm trying to tell you. Meat made the machines." "That's ridiculous. How can meat make a machine? You're asking me to believe in sentient meat." [1] http://www.eastoftheweb.com/short-stories/UBooks/TheyMade.shtml http://www.eastoftheweb.com/short-stories/UBooks/TheyMade.sh...
  - Shorel 15y ago
    Whenever I see an argument about we fully knowing how brains work, I remember some Turing-Gödel stuff that says that we would need much bigger brains to really do that. And the big brains will only be able to get an answer about smaller brains, not about themselves. So, any final answer about our brains requires far more computing power, in whatever form (mechanical or biological or whatever) than we have now.
  - mikecane 15y ago
    Or haunted beef: http://www.warrenellis.com/?p=12765 http://www.warrenellis.com/?p=12765
  - leoc 15y ago
    But Leibniz (unlike Searle, who is pretty inconsistent on this point, apparently) isn't denying or overlooking the similarity between the idea of "sentient meat" and that of sentient mill mechanisms. It's precisely the basis of his argument.
    - ugh 15y ago
      Could you explain a bit? This is how I understood the argument: Parts can’t form machines which perceive (I couldn’t find a justification for this assumption – that’s the sticking point), therefore perception is not created by parts but by a substance. The meat comment targets the first part of the argument. Leibniz seems to make an assumption (parts can’t from perceiving machines ≈ meat can’t think) which he doesn’t really justify. I thought he was using the mill as an example to show that perceiving machines made from parts are self-evidently absurd, to ridicule the idea of perceiving (or conscious) machines. What am I missing?
- davepeck 15y ago
  Let's own up to at least one basic fact: at least some portion of what we do is algorithmic -- computational -- in nature. Why? As we have this discussion, we're absorbing 1s and 0s. And we're spitting them back out in response on the other side... (what happens in the middle is left as an exercise to the reader. ;-)
  - brudgers 15y ago
    algorithmic != computational The recipe for boiled eggs is an example of a non-computational algorithm.
    - davepeck 15y ago
      I'm not quite sure what point you're making, but I should clarify mine. I wasn't trying to say anything deep. I was just making a _very_ surface observation that, at some level, our brains consume, transform, and produce bits. It's almost tautological. I abused "algorithmic" but not in the way you suggest: there are some well-defined transformations of bits that no algorithm [in the technical sense] can perform. I'll go a step further and suggest that our brains can't perform those transformations, either.
jonsen 15y ago
clockless system design with NULL convention logic: http://books.google.co.uk/books?id=UTHFcdvvHQcC http://books.google.co.uk/books?id=UTHFcdvvHQcC
- archgoon 15y ago
  Cool! As wikipedia notes, it's harder to design things this way (and apparently tends to use more transistors). But thank you, I hadn't a name to search for before. :) http://en.wikipedia.org/wiki/Asynchronous_circuit http://en.wikipedia.org/wiki/Asynchronous_circuit
  - Brashman 15y ago
    Harder is not necessarily true. It depends on what you're trying to build. In terms of QDI Async circuits, the main disadvantage is an increase in wires. In synchronous circuits, a slow enough clock ensures that the computation is completed (propagates through transistors) before moving on to the next clock cycle. For QDI async, the replacement is to have a handshaking protocol to ensure correctness as values pass through the transistors/computation. The handshaking increases the number of wires needed (and thus silicon area).

brudgers 15y ago

Whenever I see comparisons of the brain to a computer along with the implicit suggestion that computers will someday replicate brains, I am reminded of this passage from Leibniz's Monadology and that today's computers are but yesterday's mills: "Moreover, it must be confessed that perception and that which depends upon it are inexplicable on mechanical grounds, that is to say, by means of figures and motions. And supposing there were a machine, so constructed as to think, feel, and have perception, it might be conceived as increased in size, while keeping the same proportions, so that one might go into it as into a mill. That being so, we should, on examining its interior, find only parts which work one upon another, and never anything by which to explain a perception. Thus it is in a simple substance, and not in a compound or in a machine, that perception must be sought for. Further, nothing but this (namely, perceptions and their changes) can be found in a simple substance. It is also in this alone that all the internal activities of simple substances can consist." [http://philosophy.eserver.org/leibniz-monadology.txt http://philosophy.eserver.org/leibniz-monadology.txt] [http://en.wikipedia.org/wiki/Monadology http://en.wikipedia.org/wiki/Monadology]

archgoon 15y ago
Wow. Leibniz constructed the Chinese Room Argument nearly four hundred years before John Searle or computers. Nice. :)
- hasenj 15y ago
  I constructed it in my head when I was in college. I think lots of people do that; it's not a very complicated idea at all. It's just that some people wrote it down and their writings somehow became famous. When I constructed a similar argument, it was simply an argument I was having in my head with an imaginary person who was arguing with me that computers can have perception just like humans.
- brudgers 15y ago
  A homunculus is a homunculus, but nevertheless Searle's Chinese Room is perhaps a bit more radical - not so much conceptually but rather because it was proposed in contradiction to a well entrenched belief system - behaviorism.
deleted 15y ago
[deleted]
barrkel 15y ago
There is an exactly analogous argument about the human brain and its cells; and I understand the Turing test as a thought experiment that shows it to be invalid in any meaningful sense. If a machine (or a seeming person on the end of a terminal) says they perceive and think, how are you to argue otherwise? You have no evidence other humans, let alone other machines, actually can perceive or think, other than how they seem to act.
- deleted 15y ago
  [deleted]
- brudgers 15y ago
  IMO, the Turing test is conclusive to the extent one accepts Berkleyian idealism and abandons a belief in the necessity of other minds. Under those premises, solutions to the Turing test are, at this point, trivial as ELIZA long ago demonstrated. http://en.wikipedia.org/wiki/ELIZA http://en.wikipedia.org/wiki/ELIZA
  - translocation 15y ago
    I would argue that ELIZA, and the chatbots that have been programmed since, are not solutions to the Turing test. Have you ever tried holding an actual conversation with a chatbot? They almost invariably fail the real-life Turing test within two or three messages. They parse natural language incorrectly, they can't keep track of the topic of conversation, and they often reply with non-sequitor errors. Certainly, chatbots can appear to act with intelligence in certain situations. Given enough back-and-forth communication, however, a human will always realize that the bot is just parroting words and phrases that are statistically relevant to the human's questions. I don't think it's unreasonable to define Turing test success as the ability to consistently fool ordinary human beings through intelligent communication- and that, so far, has not been accomplished.
    - brudgers 15y ago
      >"Given enough back-and-forth communication, however, a human will always realize that the bot is just parroting words and phrases that are statistically relevant to the human's questions." That however is not the Turing Test at all. Here is what Turing actually wrote: I believe that in about fty years' time it will be possible, to programme computers, with a storage capacity of about 109, to make them play the imitation game so well that an average interrogator will not have more than 70 per cent chance of making the right identication after ve minutes of questioning. http://orium.homelinux.org/paper/turingai.pdf http://orium.homelinux.org/paper/turingai.pdf
adrianN 15y ago
"Thus it is in a simple substance, and not in a compound or in a machine, that perception must be sought for" This is an incorrect conclusion. You can inspect individual grains of sand as long as you want, you will never find a beach. Yet beaches are composed of sand with no magic involved.
- brudgers 15y ago
  On the other hand a beach also is part of a shoreline, and thus you will not find a beach at Great Sand Dunes National Park http://en.wikipedia.org/wiki/Great_Sand_Dunes_National_Park_and_Preserve http://en.wikipedia.org/wiki/Great_Sand_Dunes_National_Park_...
  - ugh 15y ago
    What’s your point?
    - brudgers 15y ago
      By "beach" we don't mean "many grains of sand." The parent analogy using grains does no more gets us a beach than using gears and pulleys or RAM and CPU's gets us a brain.
      - ugh 15y ago
        We mean many grains of sand in a certain configuration which are also in close proximity to many molecules of water in a certain configuration†. Do you really argue that beaches have some sort of, well, “magic”, I guess, property which makes them a beach? That seems entirely unnecessary for something as simple as beaches. You can map all the grains of sand, you can map all the molecules of water and confidently identify when something is a beach. We know how to explain beaches in terms of grains of sands and molecules of water. We cannot yet explain all properties of brains (most notably consciousness) in terms of, say, neurons but just because we cannot yet doesn’t mean we never will. †What those configurations are depends entirely on your definition of “beach”. Sand or water might also no play a role at all, again, depending on your definition.
jodrellblank 15y ago
I put a disparaging remark here, but I really shouldn't insult Leibniz based on one partial quote. More politely, I think it wrong to say "compound substances cannot be perceptive therefore humans have supernatural souls". Brains and bodies are compound substances and have perception. The next step is "I don't understand how" not "tada, souls!".
ugh 15y ago
Moreover, it must be confessed that perception and that which depends upon it are inexplicable on mechanical grounds, that is to say, by means of figures and motions. And supposing there were a machine, so constructed as to think, feel, and have perception, it might be conceived as increased in size, while keeping the same proportions, so that one might go into it as into a mill. That being so, we should, on examining its interior, find only parts which work one upon another, and never anything by which to explain a perception. That seems like too big of a leap. Why can't "parts which work one upon another" not create perception? Is this assumption justified? (I really hope the justification is not "because mills that perceive are self-evidently absurd". If it is then my next question is: Why?) If that assumption doesn't stand the rest of the argument falls flat. I would like to hear a bit more about why compound parts can't create perception. The brain certainly looks like it consists of compound parts. We obviously cannot (yet) explain consciousness so it is possible that it is impossible to create consciousness with compound parts, we just don't know. In that light Leibniz's argument seems unconvincing, at least as far as I can understand it.
- ryanklee 15y ago
  I believe that parent's point is precisely that it is indeed unconvincing and so we should in turn be mindful that our own idea that the brain is a computer will, it is possible, given further technological advances, come to strike us as just as unconvincing as Leibniz' argument. Metaphors of the brain follow along with the state of the arts of technologies. For the ancient Greeks, the human composition (they didn't talk yet of brains and consciousness) was the city-state; for early modern natural philosophers, the mill and the like; during the industrial revolution, machines; and now, with us, computers and computation. It is unlikely that our current analogy is any more or less true than previous ones, that is to say, they may be illuminating in some way and not entirely useless in our thinking about brains and consciousness, but as it goes, they are not and cannot be true because the conjectures cannot even in the end be shown to be wrong. Consciousness and the brain may not be in the end inexplicable, but I very much doubt that we will find that the brain and consciousness are something else other than the brain and consciousness, like, for instance, a mill or a computer. It would be the most surprising thing of all were we to find out that evolution produced a kind of technology before in fact that technology as a human tool was ever produced -- but that is a different argument and I'm not even sure what I mean by it.
lolcraft 15y ago
Leibniz was an idealist. He lived in peculiar ideological waters: he was Christian. He had to believe that there's the mind, there's reality, and both never touch. If he ever went out the party line, the inquisition would take care of him. According to Leibniz, neurons can't exist. Exercise does not improve your mood. Brain surgery is useless. Caffeine does not work. Hormones do nothing. Coma is unexplainable by definition. And so on. Reality killed Leibniz.
- lists 15y ago
  Actually the theory of monads bypasses the mind/body dualism by asserting a kind of synchrony. Spinoza made the same move in a different way by claiming God is the multi-dimensional plane of existence whose varying realms (mind and extension [body] being just two of an infinite number) are completely synchronousness. You're also off with the Christian comment since Leibniz wasn't within the domain of the Catholic church.
- michaeldhopkins 15y ago
  St. Luke understood the brain to be the home of mental faculty and the situation never really changed. Especially once Aristotle re-appeared, the brain was definitely understood as an organ that processes sensory input can be affected like other organs. Caffeine, exercise, possibility of surgery all known. Brain speculated to be involved in comas. Existence of neurons speculated.
ckuehne 15y ago
Whenever I see Searle's Chinese Room argument, or a version of it, invoked to show that brains cannot possibly be computers I am reminded of a passage of Terry Bison's "They're Made out of Meat" [1]: "They're made out of meat." "Meat?" "Meat. They're made out of meat." "Meat?" "There's no doubt about it. We picked up several from different parts of the planet, took them aboard our recon vessels, and probed them all the way through. They're completely meat." "That's impossible. What about the radio signals? The messages to the stars?" "They use the radio waves to talk, but the signals don't come from them. The signals come from machines." "So who made the machines? That's who we want to contact." "They made the machines. That's what I'm trying to tell you. Meat made the machines." "That's ridiculous. How can meat make a machine? You're asking me to believe in sentient meat." [1] http://www.eastoftheweb.com/short-stories/UBooks/TheyMade.shtml http://www.eastoftheweb.com/short-stories/UBooks/TheyMade.sh...
- Shorel 15y ago
  Whenever I see an argument about we fully knowing how brains work, I remember some Turing-Gödel stuff that says that we would need much bigger brains to really do that. And the big brains will only be able to get an answer about smaller brains, not about themselves. So, any final answer about our brains requires far more computing power, in whatever form (mechanical or biological or whatever) than we have now.
- mikecane 15y ago
  Or haunted beef: http://www.warrenellis.com/?p=12765 http://www.warrenellis.com/?p=12765
- leoc 15y ago
  But Leibniz (unlike Searle, who is pretty inconsistent on this point, apparently) isn't denying or overlooking the similarity between the idea of "sentient meat" and that of sentient mill mechanisms. It's precisely the basis of his argument.
  - ugh 15y ago
    Could you explain a bit? This is how I understood the argument: Parts can’t form machines which perceive (I couldn’t find a justification for this assumption – that’s the sticking point), therefore perception is not created by parts but by a substance. The meat comment targets the first part of the argument. Leibniz seems to make an assumption (parts can’t from perceiving machines ≈ meat can’t think) which he doesn’t really justify. I thought he was using the mill as an example to show that perceiving machines made from parts are self-evidently absurd, to ridicule the idea of perceiving (or conscious) machines. What am I missing?
davepeck 15y ago
Let's own up to at least one basic fact: at least some portion of what we do is algorithmic -- computational -- in nature. Why? As we have this discussion, we're absorbing 1s and 0s. And we're spitting them back out in response on the other side... (what happens in the middle is left as an exercise to the reader. ;-)
- brudgers 15y ago
  algorithmic != computational The recipe for boiled eggs is an example of a non-computational algorithm.
  - davepeck 15y ago
    I'm not quite sure what point you're making, but I should clarify mine. I wasn't trying to say anything deep. I was just making a _very_ surface observation that, at some level, our brains consume, transform, and produce bits. It's almost tautological. I abused "algorithmic" but not in the way you suggest: there are some well-defined transformations of bits that no algorithm [in the technical sense] can perform. I'll go a step further and suggest that our brains can't perform those transformations, either.

jonsen 15y ago

clockless system design with NULL convention logic: http://books.google.co.uk/books?id=UTHFcdvvHQcC http://books.google.co.uk/books?id=UTHFcdvvHQcC

archgoon 15y ago
Cool! As wikipedia notes, it's harder to design things this way (and apparently tends to use more transistors). But thank you, I hadn't a name to search for before. :) http://en.wikipedia.org/wiki/Asynchronous_circuit http://en.wikipedia.org/wiki/Asynchronous_circuit
- Brashman 15y ago
  Harder is not necessarily true. It depends on what you're trying to build. In terms of QDI Async circuits, the main disadvantage is an increase in wires. In synchronous circuits, a slow enough clock ensures that the computation is completed (propagates through transistors) before moving on to the next clock cycle. For QDI async, the replacement is to have a handshaking protocol to ensure correctness as values pass through the transistors/computation. The handshaking increases the number of wires needed (and thus silicon area).