Re: the abacus and the slide rule...

[Judith Rosen <***>]

One of the sites I found in my research on the subject of hybrid analog and digital computing technology...


 
 FROM: http://www.trnmag.com/Stories/062800/Analog_Digital_Chip_062800.html
<x-tad-bigger>Cortex chip goes both ways 
</x-tad-bigger><x-tad-smaller>By Kimberly Patch, Technology Research News

</x-tad-smaller><x-tad-smaller>In electronics, digital and analog signals are very different languages that generally don't mix. Digital circuits speak in precise ones and zeros while analog circuits speak in waves. 

The brain's neurons, however, are bilingual. 

When researchers put together a simple silicon </x-tad-smaller><x-tad-smaller>chip</x-tad-smaller><x-tad-smaller> that mimiced the brain's communication paths in a slightly different way than traditional neural nets they found something unexpected: it spoke both languages. 

</x-tad-smaller><x-tad-smaller>Digital</x-tad-smaller><x-tad-smaller> circuits use feedback to turn a switch on or off, while analog systems use feedback to amplify a signal. Traditionally, a circuit exhibits either digital or analog behavior. For example, if an amplifier has positive feedback, or a gain, of five, it will amplify an input of one to an output of five. But if the signal is too strong it will overload the system and produce a digital off. 

The cortex inspired chip, however, employed both types of signals at the same time, said researcher Rahul Sarpeshkar. "Positive feedback created explosive instability that completely shut off some neurons, but the neurons that were not shut off actually were stable and amplified their analog inputs," said Sarpeshkar, an assistant professor in the electrical engineering and computer science department at MIT and a scientific consultant for Bell Labs. 

There are a lot of potential applications for hybrid chips simply because information from sensory devices like cameras, microphones and electronic noses is voluminous and analog: "The light that you see comes in many, many shades of gray and many, many shades of intensity. The sounds that you hear come in 12 orders of magnitude of intensities, said Sarpeshkar. Today's computers convert this sensory input to digital, then process the whole mountain of data. 

Analog wave signals can, like the human brain, approximate well, but digital circuits must go through many steps of logic to do something as simple as adding one and one. It is only because digital computers run millions of steps a second that they seem fast. "Moderate precision addition can be done in analog by just hooking two signals together on a wire. It would take 3,000 transistors in digital technology to set up a circuit that would accomplish the same feat," said Sarpeshkar. 

So wholesale digital processing is "computing with needless precision on gobs and gobs of data that you don't need," he said. 

Analog signals, however, are not precise and are prone to drift, making complicated analog systems an impossibility. Digital signals are very precise and remain so even when the problem gets very complicated. Analog recordings, for instance, degrade with each copy and may eventually drift far from the original, while digital copies remain stable throughout many generations. 

A hybrid approach could potentially use analog systems to quickly and efficiently pare down large amounts of analog data to a much smaller pile, then and use its digital abilities to crunch just that data. 
-SNIP-</x-tad-smaller>







Web address: http://www.rosen-enterprises.com
BioTheory: An electronic journal of general science based on the Relational (Rosennean) Complexity Paradigm
On Oct 5, 2005, at 12:09 PM, David Macy wrote:

> <x-tad-smaller>Hey Judith,</x-tad-smaller>
>  
> <x-tad-smaller>    I'm far from an expert in anything.  I'm jack of many trades and master of none.</x-tad-smaller>
>  
> <x-tad-smaller>I did not know that there were hybrid digital/analog computational systems either.  Sounds kind of neuronal to me though.  I thought that binary was adopted because of it's minimalistic character.  What's more minimum than a base two counting system? Electricity though does not merely flow or not flow, it clearly also does so in degrees.  It seems that I remember that Faraday utilzed fluid flow analogies when contemplating electricity.  In fact when I think of an electrical component such as an inductor, I think of something like a water wheel like one might find on an old mill.</x-tad-smaller>
>  
> <x-tad-smaller>Does any of that strike you as relevant?</x-tad-smaller>
>  
> <x-tad-smaller>David</x-tad-smaller>
> > <x-tad-smaller>----- Original Message -----</x-tad-smaller>
> > <x-tad-smaller>From:</x-tad-smaller><x-tad-smaller> </x-tad-smaller><x-tad-smaller>Judith Rosen</x-tad-smaller><x-tad-smaller> </x-tad-smaller>
> > <x-tad-smaller>To:</x-tad-smaller><x-tad-smaller> </x-tad-smaller><x-tad-smaller>***</x-tad-smaller><x-tad-smaller> </x-tad-smaller>
> > <x-tad-smaller>Sent:</x-tad-smaller><x-tad-smaller> Sunday, September 25, 2005 12:50 PM</x-tad-smaller>
> > <x-tad-smaller>Subject:</x-tad-smaller><x-tad-smaller> the abacus and the slide rule...</x-tad-smaller>
> >
> > Recently I was researching the history of digital computers, which led me to look into analog computers as well. I've always considered myself "an analog girl" (preferring a complete clock-face over a digital readout and various dial controls on machines to programmable digital pushpads, etc.) so I was curious about how the notion for using a binary system came to be the accepted approach. One person I asked said it was because of the nature of electricity, which can be either on or off, so the zero represented "off" and the one represented "on". That made a bit of sense to me, but it doesn't explain the ancient use of the abacus as one of the first (known) digital computational devices. Among the nifty things I inherited from my father were his Japanese Soroban abacus and his (almost as ancient) slide rule. During my research I discovered that the slide rule is designated as an example of an analog computational device. Does anyone on the list have experience with analog computers or with hybrid computers? I hadn't realized that there are hybrid systems, but it seems to me that this would be a very good idea. Can anyone elaborate, please?
> >
> > Judith
> > Web address: http://www.rosen-enterprises.com
> > BioTheory: An electronic journal of general science based on the Relational (Rosennean) Complexity Paradigm