# A somewhat fanciful question about analog computing **URL:** \ **Category:** In My Humble Opinion\ **Created:** [May 9, 2020, 5:08am UTC](https://boards.straightdope.com/t/a-somewhat-fanciful-question-about-analog-computing/853457 "2020-05-09T05:08:56Z")\ **Posts on this page:** 12\ **Page:** 2
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [May 10, 2020, 8:51am UTC](https://boards.straightdope.com/t/a-somewhat-fanciful-question-about-analog-computing/853457/21 "2020-05-10T08:51:01Z")
> [@Voyager](#): > > I proposed in a column that we stop teaching kids that gates have nice binary signals going in, and start to show the real waveforms from the start. If nothing else, as a reminder of how amazing it is that we can build up such robust abstractions on such wobbly underpinnings. And that \*someone \*still has to think about this analog stuff, even if you don’t. > [@Voyager](#): > > BTW, as an aside, people are implementing traditional analog stuff like radio circuitry as digital, since you can then integrate it with the rest of a system, and so you can get the benefits of integration. Software Defined Radio is a lot of fun. I wrote my own SDR program, mostly from scratch, and implemented a ton of traditionally analog stuff in software. Things like phase-locked loops, IIR filters, and frequency demodulators. The experience of implementing this stuff taught me a great deal. ---
**Author:** ![DorkVader](https://avatars.discourse-cdn.com/v4/letter/d/73ab20/32.png) [@DorkVader](https://boards.straightdope.com/u/DorkVader)\ **Post date:** [May 10, 2020, 2:39pm UTC](https://boards.straightdope.com/t/a-somewhat-fanciful-question-about-analog-computing/853457/22 "2020-05-10T14:39:25Z")
> [@Lumpy](#): > > That’s kinda’ unfair, given that the individual transistor elements in modern chips are tens of nanometers. There was some talk of using the same micro-fabrication techniques used to make computer chips to make micron-scale mechanical parts for special purpose (i.e. ultra-radiation resistant) computers. Maybe, but I was really curious about how a mechanical computing system built with parts that could aren’t micro- or nanoscopic would look, if was comparable to a modern computer in function > [@Dr.Strangelove](#): > > If nothing else, as a reminder of how amazing it is that we can build up such robust abstractions on such wobbly underpinnings. And that \*someone \*still has to think about this analog stuff, even if you don’t. It is interesting, and can be fun to talk about, but yes in the end a bit of whimsy ---
**Author:** ![Andy\_L](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Andy\_L](https://boards.straightdope.com/u/Andy_L)\ **Post date:** [May 10, 2020, 2:40pm UTC](https://boards.straightdope.com/t/a-somewhat-fanciful-question-about-analog-computing/853457/23 "2020-05-10T14:40:58Z")
> [@EinsteinsHund](#): > > Did it also have a big representational switch board, like a big white board, with inputs and outputs next to symbols on the board representing integrators and such? That’s how I remember the interface, but I have no idea how the hardware behind it really looked. Yes (as best I remember) ---
**Author:** ![Andy\_L](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Andy\_L](https://boards.straightdope.com/u/Andy_L)\ **Post date:** [May 10, 2020, 2:47pm UTC](https://boards.straightdope.com/t/a-somewhat-fanciful-question-about-analog-computing/853457/24 "2020-05-10T14:47:29Z")
Actually this picture is a lot like the one I remember [Analog computer - Wikipedia](https://en.wikipedia.org/wiki/Analog_computer#/media/File:PACE-TR-10_analog_computer_-_National_Cryptologic_Museum_-_DSC07908.JPG) - I remember the little connectors linking the components. ---
**Author:** ![EinsteinsHund](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/einsteinshund/32/8400_2.png) [@EinsteinsHund](https://boards.straightdope.com/u/EinsteinsHund)\ **Post date:** [May 10, 2020, 5:29pm UTC](https://boards.straightdope.com/t/a-somewhat-fanciful-question-about-analog-computing/853457/25 "2020-05-10T17:29:13Z")
> [@Andy\_L](#): > > Actually this picture is a lot like the one I remember [Analog computer - Wikipedia](https://en.wikipedia.org/wiki/Analog_computer#/media/File:PACE-TR-10_analog_computer_-_National_Cryptologic_Museum_-_DSC07908.JPG) - I remember the little connectors linking the components. Yes, that looks similar to what I remember. ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [May 10, 2020, 7:38pm UTC](https://boards.straightdope.com/t/a-somewhat-fanciful-question-about-analog-computing/853457/26 "2020-05-10T19:38:53Z")
For about two years in the mid 50s, I was responsible for the operations of a rather large analog computer. It was specialized to solve systems of up to 7 simultaneous differential equations of the form dx\_i/dt = f\_i(x\_1,…,x\_7) where the functions were linear combinations of linear and quadratic terms, that is k\_jx\_j and l\_jkx\_jx\_k where the k’s and l’s are constants. (Any chemist will recognize these equations as chemical reaction equations.) The machine, made up of operational amplifier packages made up of subminiature vacuum tubes, occupied 7 consoles each about 2 feet wide and 7 feet high. Programming was by running phono cables from outputs to inputs and was trivial. My main job was repairing the op amps. Addition, subtraction, and integration were trivial. Multiplication of two variables was a kludge, based on an approximate squarer and the quarter square identity: xy = (1/4)((x+y)^2 - (x-y)^2)). It operated on a 5 Khz square wave. You could obviously build an analog Turing machine, but to match the computational ability of your phone, it would probably be the size of a continent and take the age of the universe to do any significant computation. ---
**Author:** ![Andy\_L](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Andy\_L](https://boards.straightdope.com/u/Andy_L)\ **Post date:** [May 10, 2020, 8:55pm UTC](https://boards.straightdope.com/t/a-somewhat-fanciful-question-about-analog-computing/853457/27 "2020-05-10T20:55:13Z")
Analog tide prediction machines were apparently used up until the 1970s to (as you might expect) predict tides [Tide-predicting machine - Wikipedia](https://en.wikipedia.org/wiki/Tide-predicting_machine) ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [May 10, 2020, 8:59pm UTC](https://boards.straightdope.com/t/a-somewhat-fanciful-question-about-analog-computing/853457/28 "2020-05-10T20:59:09Z")
> [@peccavi](#): > > […] > > **Analog circuits** are just circuits that have a smooth continuum of “output” values as “input” values change rather than being restricted to only a limited number of states (usually two, but multi-level digital logic is a thing) in a digital circuit. However, fundamentally, all digital gates in a computer are analog circuits (well, even more fundamentally everything’s a quantum system), but the smooth continuous values are made to be probabilistically negligible and the “high” and “low” values almost invariably the result of inputs. But all the elements are analog, and analog effects can occur, usually screwing up the result. > > […] I think “analog” in the context of computing means not that there are continuously variable voltages and/or currents at the most immediate level in the behavior of the circuits, but that the value of a single voltage or current scaled over its possible engineering range is an analog or proxy for some other value of interest. In “analog” circuits there is an “analogy” between the voltage here and some different value in the real world, such as temperature or pressure or altitude or position of a machine part. The fact that even in digital computers the lowest level components operate over continuous ranges of voltage or current isn’t the same sense of “analog”. And none of those voltages, by themselves, are meant to represent continuous variables out in the real world; they only do so in groups according to a somewhat arbitrary logical code such as IEEE 754 formatted 32 bit floats. ---
**Author:** ![Voyager](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/voyager/32/133_2.png) [@Voyager](https://boards.straightdope.com/u/Voyager)\ **Post date:** [May 10, 2020, 10:48pm UTC](https://boards.straightdope.com/t/a-somewhat-fanciful-question-about-analog-computing/853457/29 "2020-05-10T22:48:27Z")
> [@Lumpy](#): > > That’s kinda’ unfair, given that the individual transistor elements in modern chips are tens of nanometers. There was some talk of using the same micro-fabrication techniques used to make computer chips to make micron-scale mechanical parts for special purpose (i.e. ultra-radiation resistant) computers. That’s know stuff, called [MEMS](https://internetofthingsagenda.techtarget.com/definition/micro-electromechanical-systems-MEMS). 10 years or so back we had lots of sessions on how to test them. As I understand it, the chip inside your airbag system uses them for one. So production technology at the moment. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [May 10, 2020, 11:12pm UTC](https://boards.straightdope.com/t/a-somewhat-fanciful-question-about-analog-computing/853457/30 "2020-05-10T23:12:46Z")
> [@Voyager](#): > > As I understand it, the chip inside your airbag system uses them for one. So production technology at the moment. Indeed–the accelerometers and gyroscopes in every phone also use MEMS. Some main oscillators also use MEMS instead of quartz. There was an amusing incident a short while ago where a helium leak from an MRI machine killed every iPhone in the hospital. The helium infiltrated the MEMS oscillator and changed the resonant frequency enough to kill it (temporarily, until the oscillators could be “aired out”). I’m not aware of anyone using MEMS for actual computation, but it could be done. ---
**Author:** ![N9IWP](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/n9iwp/32/3154_2.png) [@N9IWP](https://boards.straightdope.com/u/N9IWP)\ **Post date:** [May 26, 2020, 12:34pm UTC](https://boards.straightdope.com/t/a-somewhat-fanciful-question-about-analog-computing/853457/31 "2020-05-26T12:34:56Z")
Recent reprint Ars Technica article on analog computers: > **[Gears of war: When mechanical analog computers ruled the waves](https://arstechnica.com/information-technology/2020/05/gears-of-war-when-mechanical-analog-computers-ruled-the-waves/)** > > From the archives: In some ways, new Navy computers fall short of the power of 1930s tech. Brian ---
**Author:** ![Andy\_L](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Andy\_L](https://boards.straightdope.com/u/Andy_L)\ **Post date:** [May 26, 2020, 5:04pm UTC](https://boards.straightdope.com/t/a-somewhat-fanciful-question-about-analog-computing/853457/32 "2020-05-26T17:04:14Z")
> [@N9IWP](#): > > Recent reprint Ars Technica article on analog computers: > [Gears of war: When mechanical analog computers ruled the waves | Ars Technica](https://arstechnica.com/information-technology/2020/05/gears-of-war-when-mechanical-analog-computers-ruled-the-waves/) > > Brian Thanks [Previous page](https://boards.straightdope.com/t/a-somewhat-fanciful-question-about-analog-computing/853457.md?page=1)