5 ms·

What Is Analog Computing?

49 points by walterbell 2y ago

AlexDragusin 2y ago
The article ends flat and abruptly, I was setting myself for a long and nice journey in the style of Quanta Magazine, what happened?
- signalToNose 2y ago
  Reader version on mobile seem broken. Hiding reader show a longer article
  - AlexDragusin 2y ago
    I don't think so, it ends like this: "The advantages of digital computing are real, but so are the drawbacks. Perhaps, by reaching back to computing’s past, researchers will be able to steer a sustainable path toward our computational future. Correction: August 2, 2024: The $100 billion data center would require 5 gigawatts of power, not 5 megawatts." So it's the end of the article indeed.
    - walterbell 2y ago
      Encore! Encore!
adrianN 2y ago
The internet archive has this interesting educational film about mechanical computers on ships: https://archive.org/details/27794FireControlComputersPt1 https://archive.org/details/27794FireControlComputersPt1
- bloopernova 2y ago
  I've been reading a lot recently about the World War 2 Pacific naval conflict. The things done with mechanical fire controllers was amazing! The US has radar linked anti-aircraft and surface guns, plus radar proximity shells, all mechanical/analogue driven. Thank you for the link! :)
cduzz 2y ago
Why do computers have clocks? So they don't have to do everything at once. (the joke is that analog computers don't have clocks... Do they?)
- walterbell 2y ago
  > analog computers don't have clocks Laws of Physics?
- JKCalhoun 2y ago
  The old jumper-wire style analog computers I'm envisioning did not have a clock to my knowledge [1]. Does the animal brain have a clock? [1] ChatGPT says otherwise — says, yes, they did have a clock of sorts. I'm wondering if something like a voltage sweep (triangle or sine wave?) would be a kind of "clock input" for an analog computer though.
  - imtringued 2y ago
    I would assume that neurons would behave more like a wavefront processor, but even this analogy is still a big stretch.
  - zabzonk 2y ago
    i sort of maintained one them back in the early 80s and i seem to remember that it packed a wave generator as one of its inputs, which could kind of be used as a clock. but don't quote me - i'm strictly a digital guy!
- dragontamer 2y ago
  > (the joke is that analog computers don't have clocks... Do they?) Not a digital clock, no. But your modem controller (2.4GHz, 5GHz or whatever) has a frequency that the radio analog chips are adding, multiplying, exponenting and decimating to pull the data out of the radio waves. And computation to pull data out of (or push data into) a 2.4GHz channel is best done with analog today. Sure, SDR exists but its far more expensive than some PLLs and other analog techniques.
nbingham 2y ago
The reason we ended up with digital logic is because of noise. Hysteresis from digital gates was the only way to make such large systems from such small devices without all of our signaling turning into a garbled mess. Analog processing has its niches and I suspect the biggest niche will be where that noise is a feature rather than a hindrance, something like continuous time neutral networks.
- stefanka 2y ago
  Neuromorphic hardware is an area where I encountered analogue computing [1]. Biological neurons would be modeled by a leaky integration (resistor/capacitator) unit. The system was 1*10^5 times faster than real-time—too fast to use it for robotics—and consumed little power but was sensitive to temperature (much as our brains). If I recall correctly, the technology has been used at cern, as digital HW would have required too high clock speeds. I have no clue what happened to the technology but there were other attempts at neuromorphic, analogue hardware. It was very exciting to observe and use this research! [1]https://brainscales.kip.uni-heidelberg.de/ https://brainscales.kip.uni-heidelberg.de/ edit: newer link: https://open-neuromorphic.org/neuromorphic-computing/hardware/brainscales-2-universitat-heidelberg/ https://open-neuromorphic.org/neuromorphic-computing/hardwar...
  - nbingham 2y ago
    I worked on a similar project - the Stanford braindrop chip. It's a really interesting technology, what happened is that most people don't really know how to train those systems. There's a group called Vivum that seems to have a solution. I work with QDI systems, and I've long suspected that it would be possible to use those same design principles to make analog circuits robust to timing variation. QDI design is about sequencing discrete events using digital operators - AND and OR. I wonder if it is possible to do the same with continuous "events" using the equivalent analog operators, mix and sum.
    - stefanka 2y ago
      We got some nice results with spiking/pulsed networks but the small number of units limits the application so we usually end up in a simulator or using more abstract models. There seems to be a commercial product but also only with 0.5K neurons, might be enough for 1D data processing though and filling a good niche there (1mW!) [2] [2] https://open-neuromorphic.org/neuromorphic-computing/hardware/snp-by-innatera/ https://open-neuromorphic.org/neuromorphic-computing/hardwar...
jerf 2y ago
This is one of those things I don't get why people go so gaga over them. The article starts with: "But it’s not obvious why a system that operates using discrete chunks of information would be good at modeling our continuous, analog world." OK, fine. But, if my "discrete" modelling is using 64 bits of precision, or, in decimal, about 19 digits of precision, and your analog system on a good day has about 3, how could your analog system even "tell" mine is discrete? It can't "see" that finely in the first place. Oh, you don't like how it's excessively precise? It is off-the-shelf numerical tech to include precision in calculations. It isn't something every programmer knows, but it's been in books for years. Oh, by the way, it is also off-the-shelf numerical tech to estimate errors using digital computers. That's going to be a hard trick to match in your analog system. Also, digital systems offer many tradeoffs with regard to error levels and computation time. Another thing your analog system is going to have a hard time with. "But floating point numbers have lots of problems with instability and such." Most of those problems will manifest in your analog computers, too. Many of those aren't so much about floating point per se as just doing inadvisable things with numbers in general, e.g., if you set up an analog computer to subtract two quantities that come out "close to zero" and then divide by that quantity, your analog computer is going to behave in much the same way that a digital computer would. Ye Olde Classic "add a whole bunch of small numbers together only for them all to disappear because of the large number" is also the sort of problem that you can only get because digital is good enough to reveal it in the first place; accurate adding together millions of very tiny numbers is something your analog computer almost certainly just plain can't do at all. A carefully crafted analog system might be able to outpace a digital system, but it's not going to be the norm. Normally the digital system will outpace the analog system by absurd amounts. Now, are there niche cases where analog may be interesting? Yes, absolutely. Neural nets is an interesting possibility. Obviously a big possibility. There's a handful of others. But it's a niche within a niche. There's no problem with that. There's plenty of interesting niches within niches. You can make careers in a niche within a niche. But I don't know what it is about this one that convinces so many people that there's some sort of revolution budding and we're on the cusp of an amazing new era of analog computing that will do so many amazing things for everyone... as opposed to a niche within a niche. We had that revolution. It was digital computing. It is the single largest revolution in the history of man as measured by factors of magnitude of improvement from start to now, and the ditigal revolution is still not done. Analog is not going to overtake that. It doesn't have the headroom. It doesn't have the orders of magnitude improvement possible. That's why it was left behind in the first place. The delta between my kid 3D printing a clock mechanism and the finest Swiss watchmaker who ever lived is still a small single digit number of orders of magnitude in terms of their mechanical precision, and in the digital world we still expect that degree of progress about every 5-10 years or so... and that's slower than it was for many decades.
dragontamer 2y ago
OpAmps are still one of the most common chips used today, and one of the most obvious analog computers in use. And yet not even one paragraph in this article?
nickpsecurity 2y ago
Here’s an example of a general purpose, analog computer: https://museum.syssrc.com/artifact/exhibits/251/ https://museum.syssrc.com/artifact/exhibits/251/ I’ll note that there’s been plenty of work on general-purpose, analog computing. Analog’s competitiveness also lives on in mixed-signal ASIC’s. The problem with new products, though, is analog requires fully-custom, circuit design. Outside some niche uses, you can’t just synthesize them from higher-level specs like you can digital designs with standard cells. That puts analog at a severe disadvantage on NRE cost. Especially as both design rules and mask costs increase with every node shrink.
- KK7NIL 2y ago
  Indeed, analog circuits are much more process sensitive (while digital circuits are defect sensitive), which makes their design slower and much more closely coupled to the specific process node that is being targeted. This is why now a days bleeding edge process nodes might be lacking in IO (especially fast serial IO) when they're first released. Additionally, analog just hasn't scaled for quite a while now. Even traditionally analog circuits like PLL's and IO are getting more and more digital as the digital scaling is making more digital architectures competitive in space and power when they weren't before.
HarHarVeryFunny 2y ago
It's interesting that analog computers embody both meanings of "analog" - that of continuous quantities vs discrete/digital ones, and also of one thing being comparable to ("an analog of", cf analogy) something else. The article seems to put a bit of a silly spin on an interesting subject by wanting to present analog computers as a potential alternative to digital ones, when in fact that is only rarely going to be possible. Digital computers support programming - solving of problems by describing the process by which they are to be solved, whereas analog computers instead support solving of (limited types) of problem by building an analog of the problem (which you could think of as "describing" the problem, rather than how to solve it), either using analog electronics (a patch panel analog computer), or by building a physical analog of it such as the Antikythera mechanism which models the motions of the planets. The article oddly omits any mention of quantum computers which (unless I'm totally misguided!) are essentially a type of analog computer - one that is no replacement for digital computers and general problem solving since it can't be programmed, but rather only works when one can configure it to be an analog of the problem to be solved. As with any other type of analog computer, the problem is then solved by letting the system run and the dynamics play out.
- radarsat1 2y ago
  Isn't that where the term analog for continuous values comes from though? That they are voltages that vary in proportion to physical quantities? And therefore analogous to those quantities.
  - HarHarVeryFunny 2y ago
    Makes sense - I was wondering about the connection, but lazily looking up the etymology of the word didn't provide any obvious answer.
  - jkaptur 2y ago
    Yep: https://english.stackexchange.com/questions/241379/what-is-the-origin-of-analogue-as-a-term-meaning-non-digital https://english.stackexchange.com/questions/241379/what-is-t...
- 2y ago
_glass 2y ago
I would say an analog synthesizer is an analog computer. The input are for example voltages to simulate notes, and the computational output is a waveform. I prefer analog because digital synthesizer, at least for Subtractive synthesis, are only a simulation of the real instrument. The downsides are not unlike other analog computers, noise and dependence on temperature distort the output.
sholladay 2y ago
Veritasium has a good video about analog computers. It covers how they work, what they are used for, pros and cons compared to digital, what they look like today, a bit of the history and their possible future. https://youtu.be/GVsUOuSjvcg https://youtu.be/GVsUOuSjvcg

49 points by walterbell 2y ago

The article ends flat and abruptly, I was setting myself for a long and nice journey in the style of Quanta Magazine, what happened?

signalToNose 2y ago
Reader version on mobile seem broken. Hiding reader show a longer article
- AlexDragusin 2y ago
  I don't think so, it ends like this: "The advantages of digital computing are real, but so are the drawbacks. Perhaps, by reaching back to computing’s past, researchers will be able to steer a sustainable path toward our computational future. Correction: August 2, 2024: The $100 billion data center would require 5 gigawatts of power, not 5 megawatts." So it's the end of the article indeed.
  - walterbell 2y ago
    Encore! Encore!

adrianN 2y ago

The internet archive has this interesting educational film about mechanical computers on ships: https://archive.org/details/27794FireControlComputersPt1 https://archive.org/details/27794FireControlComputersPt1

bloopernova 2y ago
I've been reading a lot recently about the World War 2 Pacific naval conflict. The things done with mechanical fire controllers was amazing! The US has radar linked anti-aircraft and surface guns, plus radar proximity shells, all mechanical/analogue driven. Thank you for the link! :)

cduzz 2y ago

Why do computers have clocks? So they don't have to do everything at once. (the joke is that analog computers don't have clocks... Do they?)

walterbell 2y ago
> analog computers don't have clocks Laws of Physics?
JKCalhoun 2y ago
The old jumper-wire style analog computers I'm envisioning did not have a clock to my knowledge [1]. Does the animal brain have a clock? [1] ChatGPT says otherwise — says, yes, they did have a clock of sorts. I'm wondering if something like a voltage sweep (triangle or sine wave?) would be a kind of "clock input" for an analog computer though.
- imtringued 2y ago
  I would assume that neurons would behave more like a wavefront processor, but even this analogy is still a big stretch.
- zabzonk 2y ago
  i sort of maintained one them back in the early 80s and i seem to remember that it packed a wave generator as one of its inputs, which could kind of be used as a clock. but don't quote me - i'm strictly a digital guy!
dragontamer 2y ago
> (the joke is that analog computers don't have clocks... Do they?) Not a digital clock, no. But your modem controller (2.4GHz, 5GHz or whatever) has a frequency that the radio analog chips are adding, multiplying, exponenting and decimating to pull the data out of the radio waves. And computation to pull data out of (or push data into) a 2.4GHz channel is best done with analog today. Sure, SDR exists but its far more expensive than some PLLs and other analog techniques.

nbingham 2y ago

The reason we ended up with digital logic is because of noise. Hysteresis from digital gates was the only way to make such large systems from such small devices without all of our signaling turning into a garbled mess. Analog processing has its niches and I suspect the biggest niche will be where that noise is a feature rather than a hindrance, something like continuous time neutral networks.

stefanka 2y ago
Neuromorphic hardware is an area where I encountered analogue computing [1]. Biological neurons would be modeled by a leaky integration (resistor/capacitator) unit. The system was 1*10^5 times faster than real-time—too fast to use it for robotics—and consumed little power but was sensitive to temperature (much as our brains). If I recall correctly, the technology has been used at cern, as digital HW would have required too high clock speeds. I have no clue what happened to the technology but there were other attempts at neuromorphic, analogue hardware. It was very exciting to observe and use this research! [1]https://brainscales.kip.uni-heidelberg.de/ https://brainscales.kip.uni-heidelberg.de/ edit: newer link: https://open-neuromorphic.org/neuromorphic-computing/hardware/brainscales-2-universitat-heidelberg/ https://open-neuromorphic.org/neuromorphic-computing/hardwar...
- nbingham 2y ago
  I worked on a similar project - the Stanford braindrop chip. It's a really interesting technology, what happened is that most people don't really know how to train those systems. There's a group called Vivum that seems to have a solution. I work with QDI systems, and I've long suspected that it would be possible to use those same design principles to make analog circuits robust to timing variation. QDI design is about sequencing discrete events using digital operators - AND and OR. I wonder if it is possible to do the same with continuous "events" using the equivalent analog operators, mix and sum.
  - stefanka 2y ago
    We got some nice results with spiking/pulsed networks but the small number of units limits the application so we usually end up in a simulator or using more abstract models. There seems to be a commercial product but also only with 0.5K neurons, might be enough for 1D data processing though and filling a good niche there (1mW!) [2] [2] https://open-neuromorphic.org/neuromorphic-computing/hardware/snp-by-innatera/ https://open-neuromorphic.org/neuromorphic-computing/hardwar...

jerf 2y ago

This is one of those things I don't get why people go so gaga over them. The article starts with: "But it’s not obvious why a system that operates using discrete chunks of information would be good at modeling our continuous, analog world." OK, fine. But, if my "discrete" modelling is using 64 bits of precision, or, in decimal, about 19 digits of precision, and your analog system on a good day has about 3, how could your analog system even "tell" mine is discrete? It can't "see" that finely in the first place. Oh, you don't like how it's excessively precise? It is off-the-shelf numerical tech to include precision in calculations. It isn't something every programmer knows, but it's been in books for years. Oh, by the way, it is also off-the-shelf numerical tech to estimate errors using digital computers. That's going to be a hard trick to match in your analog system. Also, digital systems offer many tradeoffs with regard to error levels and computation time. Another thing your analog system is going to have a hard time with. "But floating point numbers have lots of problems with instability and such." Most of those problems will manifest in your analog computers, too. Many of those aren't so much about floating point per se as just doing inadvisable things with numbers in general, e.g., if you set up an analog computer to subtract two quantities that come out "close to zero" and then divide by that quantity, your analog computer is going to behave in much the same way that a digital computer would. Ye Olde Classic "add a whole bunch of small numbers together only for them all to disappear because of the large number" is also the sort of problem that you can only get because digital is good enough to reveal it in the first place; accurate adding together millions of very tiny numbers is something your analog computer almost certainly just plain can't do at all. A carefully crafted analog system might be able to outpace a digital system, but it's not going to be the norm. Normally the digital system will outpace the analog system by absurd amounts. Now, are there niche cases where analog may be interesting? Yes, absolutely. Neural nets is an interesting possibility. Obviously a big possibility. There's a handful of others. But it's a niche within a niche. There's no problem with that. There's plenty of interesting niches within niches. You can make careers in a niche within a niche. But I don't know what it is about this one that convinces so many people that there's some sort of revolution budding and we're on the cusp of an amazing new era of analog computing that will do so many amazing things for everyone... as opposed to a niche within a niche. We had that revolution. It was digital computing. It is the single largest revolution in the history of man as measured by factors of magnitude of improvement from start to now, and the ditigal revolution is still not done. Analog is not going to overtake that. It doesn't have the headroom. It doesn't have the orders of magnitude improvement possible. That's why it was left behind in the first place. The delta between my kid 3D printing a clock mechanism and the finest Swiss watchmaker who ever lived is still a small single digit number of orders of magnitude in terms of their mechanical precision, and in the digital world we still expect that degree of progress about every 5-10 years or so... and that's slower than it was for many decades.

dragontamer 2y ago

OpAmps are still one of the most common chips used today, and one of the most obvious analog computers in use. And yet not even one paragraph in this article?

nickpsecurity 2y ago

Here’s an example of a general purpose, analog computer: https://museum.syssrc.com/artifact/exhibits/251/ https://museum.syssrc.com/artifact/exhibits/251/ I’ll note that there’s been plenty of work on general-purpose, analog computing. Analog’s competitiveness also lives on in mixed-signal ASIC’s. The problem with new products, though, is analog requires fully-custom, circuit design. Outside some niche uses, you can’t just synthesize them from higher-level specs like you can digital designs with standard cells. That puts analog at a severe disadvantage on NRE cost. Especially as both design rules and mask costs increase with every node shrink.

KK7NIL 2y ago
Indeed, analog circuits are much more process sensitive (while digital circuits are defect sensitive), which makes their design slower and much more closely coupled to the specific process node that is being targeted. This is why now a days bleeding edge process nodes might be lacking in IO (especially fast serial IO) when they're first released. Additionally, analog just hasn't scaled for quite a while now. Even traditionally analog circuits like PLL's and IO are getting more and more digital as the digital scaling is making more digital architectures competitive in space and power when they weren't before.

HarHarVeryFunny 2y ago

It's interesting that analog computers embody both meanings of "analog" - that of continuous quantities vs discrete/digital ones, and also of one thing being comparable to ("an analog of", cf analogy) something else. The article seems to put a bit of a silly spin on an interesting subject by wanting to present analog computers as a potential alternative to digital ones, when in fact that is only rarely going to be possible. Digital computers support programming - solving of problems by describing the process by which they are to be solved, whereas analog computers instead support solving of (limited types) of problem by building an analog of the problem (which you could think of as "describing" the problem, rather than how to solve it), either using analog electronics (a patch panel analog computer), or by building a physical analog of it such as the Antikythera mechanism which models the motions of the planets. The article oddly omits any mention of quantum computers which (unless I'm totally misguided!) are essentially a type of analog computer - one that is no replacement for digital computers and general problem solving since it can't be programmed, but rather only works when one can configure it to be an analog of the problem to be solved. As with any other type of analog computer, the problem is then solved by letting the system run and the dynamics play out.

radarsat1 2y ago
Isn't that where the term analog for continuous values comes from though? That they are voltages that vary in proportion to physical quantities? And therefore analogous to those quantities.
- HarHarVeryFunny 2y ago
  Makes sense - I was wondering about the connection, but lazily looking up the etymology of the word didn't provide any obvious answer.
- jkaptur 2y ago
  Yep: https://english.stackexchange.com/questions/241379/what-is-the-origin-of-analogue-as-a-term-meaning-non-digital https://english.stackexchange.com/questions/241379/what-is-t...
2y ago

_glass 2y ago

I would say an analog synthesizer is an analog computer. The input are for example voltages to simulate notes, and the computational output is a waveform. I prefer analog because digital synthesizer, at least for Subtractive synthesis, are only a simulation of the real instrument. The downsides are not unlike other analog computers, noise and dependence on temperature distort the output.

sholladay 2y ago

Veritasium has a good video about analog computers. It covers how they work, what they are used for, pros and cons compared to digital, what they look like today, a bit of the history and their possible future. https://youtu.be/GVsUOuSjvcg https://youtu.be/GVsUOuSjvcg