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The Last Millimetre

Almost entirely photonic computer
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I have received a message from myself in 1978, who has asked me to post this on here. I thought I already had but considerable perusal of my page suggests that I haven't, so here it is:

Consider the computer, with its tape drives, terminal, disc packs and blinking lights, oh, and its wiring, along which signals move rather slower than necessary. Or, better, consider the computer as we know it, with its 6502 CPU and PCB covered in TTL integrated circuits and stuff. Replace all the external wiring to the chips and integrated circuits with fibre optics and attach semiconductor lasers and photocells to the very last bits of the circuits which absolutely must use electricity. This will increase the velocity of the signals to the speed of light in the appropriate medium. Where possible, replace a wire with a laser beam moving through a vacuum.

There's some stuff here about one-way glass being analogous to semiconductors but at the time I was only eleven so that's forgivable. Having said that, is there a way of using fluorescence to implement logic gates?

Achieve a display using the actual lasers themselves projected onto a wall or other screen device, thereby eliminating the need for any electronic display at all.

Now the questions: Have I in fact posted this before? I did post something about replacing an electricity supply with light.

Would this really make a lot of difference to processing speed? I suspect it wouldn't, and also that many of the components which are currently smaller than a wavelength of red light would have to be larger. It also sounds like it would use a lot of power. On the other hand, fibre optics does seem to speed up the internet, so maybe.

nineteenthly, Jan 23 2017

Two-photon absorption https://en.wikipedi...o-photon_absorption
A nonlinear optical phenomenon that could be useful for // Having said that, is there a way of using fluorescence to implement logic gates? // [notexactly, Feb 26 2017]

Saturable absorption https://en.wikipedi...aturable_absorption
Another NLO phenomenon that could be useful for the same purpose. Maybe you could even make a saturable absorber function as a NOT gate, possibly by adding two-photon sensitivity somehow? [notexactly, Feb 26 2017]

The Machine Stops https://en.wikipedi...i/The_Machine_Stops
Short story that predicted something like the Internet, complete with video chat. Link to full text in the external links section. At my old university I attended a production of "The Machine Starts", which was an interactive play written by the students as a prequel to this story. [notexactly, Feb 26 2017]

Memex https://en.wikipedia.org/wiki/Memex
Hypothetical proto-hypertext system described by Vannevar Bush in 1945. An alternative imagining of what might have been instead of the Internet. [notexactly, Feb 26 2017]

Data written on paper, read by fire. Also the idea of burning-paper logic. https://www.youtube...watch?v=eafEPGx-9rE
// I wonder why we didn't invent paper computers first? // & // It occurs to me, in fact, that even making the right pencil marks on paper ought to be able to do some data processing // [notexactly, Feb 26 2017]

We did that. https://en.wikipedia.org/wiki/Dekatron
// I would've thought that the earliest attempts at electronic computers would either involve attempts to replicate mechanical calculators using circuits (e.g. something which stores digits in the electronic equivalent of a dial which then trips the next dial when it goes round the clock like an odometer) […] // [notexactly, Feb 26 2017]

We did that too. http://www.ee.ryers...s/relay-counter.pdf
// […] or relays. // [notexactly, Feb 26 2017]

Technology for a better fire computer http://www.sparkban...me-amp/flameamp.htm
I should have remembered this the other week. See next link for where I saw this again. [notexactly, Mar 11 2017]

Electrolytic diodes made with baking soda https://hackaday.co...-7-segment-display/
A comment from [Hales] (the maker of the baking soda diodes) gave the link immediately above. [notexactly, Mar 11 2017]

[link]






       //I have received a message from myself in 1978// - Does the medium you received this message through allow two-way conversations? If so, you could make a lot of money.
hippo, Jan 23 2017
  

       //if so, you could make a lot of money//   

       [marked-for-tagline]
theircompetitor, Jan 23 2017
  

       I've had a debate with myself about that but haven't heard anything back yet. I'll let you know when I do.
nineteenthly, Jan 23 2017
  

       You can actually go quite a bit further than just moving signal around optically, you can actually do some computing. There's a few ways of doing it too. You can fire a light beam at a 45 degree half silvered mirror, half your light passes straight through and half is reflected. Put a detector at both end points, now you have an AND gate. By meddling around with fluorescence, you can for example, illuminate a red fluorescent quantum dot with either a UV, blue, green, or orange light and get red output from all of them. That's a single molecule triple AND gate. If you have something really dull to do, you can spend a whole afternoon avoiding it by designing all of the logic gates with single/dual molecule sizes, all operating at the speed of light. Then you realize you've invented optical computing. Unfortunately, that's already been invented.
bs0u0155, Jan 23 2017
  

       While the 6502 microprocessor was only 3 years old in 1978, the HalfBakery didn't exist back then. How could you have known of it to tell yourself to post a message to it? Perhaps you did receive a message from the future?   

       Oh, and as for this Idea, you are not accounting for the time it takes to convert signals from one medium to another and back again (electric signals to photon signals to electric signals). To achieve maximum speed, all the circuitry needs to be photonic, not just the interconnects.
Vernon, Jan 23 2017
  

       Plus even a typical 1978 6502 microcomputer would have had more 4000 series CMOS in than just to consist of only bipolar 7400 series TTL. Compared to 7400 4000 series is easier to design for from a power and fan out point of view, and affords lower current requirements for the whole board.
Ian Tindale, Jan 23 2017
  

       In fact, [Vernon], that was very much in my mind and it's a question I'm kind of asking by posting this. How much difference would it make?   

       [Ian], right, okay, I think I was thinking of an Apple ][ PCB and not noticing what the chips were but assuming they were 74LS doobries. Not having an Apple ][ handy at the time, I had to guess.   

       [bs0u0155] thanks, I've long wondered about it. I imagine it might be a bit similar to fluidic logic in that there would be certain things which are undoable. For instance, you mention AND gates but not inverters and that's not enough for functional completeness although I imagine some of it is.   

       [Vernon] again: Something like the internet is predictable from way off. Tomorrow's World and Profiles Of The Future both mention something similar and Asimov's Multivac has similar qualities. The internet seems to be one of the most predictable inventions ever. The question is though, how much detail in the internet is predictable? Could I have imagined an ideas bank? Not sure. I did write a lot of stuff down though.
nineteenthly, Jan 24 2017
  

       Multifrequencies or a holistic component might be easier to implement in light.
wjt, Jan 25 2017
  

       I wonder why we didn't invent paper computers first? I mean, it'd be possible to dope areas of the paper to be conductors, as well as dope other areas as semiconductors, leaving the remaining areas insulators. It seems so obvious rather than making the very strange leap into valves, which seems to completely reek of the same irreducible complexity argument that causes shit for brains morons to not believe that eyes or ears or outboard motors could ever evolve.
Ian Tindale, Jan 25 2017
  

       It occurs to me, in fact, that even making the right pencil marks on paper ought to be able to do some data processing because graphite can to some extent conduct electricity and you can adjust a CPU's clock speed with a pencil mark because of that. However, I would've thought that the earliest attempts at electronic computers would either involve attempts to replicate mechanical calculators using circuits (e.g. something which stores digits in the electronic equivalent of a dial which then trips the next dial when it goes round the clock like an odometer) or relays.   

       Also, I wonder about how feasible making a computer out of silver on a glass plate photographically would be, as far back as the nineteenth century.
nineteenthly, Jan 25 2017
  

       Maybe there's a particular scene out there that forms a viable processor when photographed? As luck would have it, it was never photographed, or at least, not from the correct angle, field of view, exposure index and focal length.
Ian Tindale, Jan 25 2017
  

       Wow! That's true. Wouldn't it be amazing if there was a city somewhere which turned out to be a CPU if photographed from the air?
nineteenthly, Jan 25 2017
  

       //Maybe there's a particular scene out there that forms a viable processor when photographed?//   

       Maybe some weird photoelectric effect has provided an energy source to enable some photographs to become sentient. That 50's picture of the rowing team hanging in the club house could be thinking "Why is it so dark? Where am I?".
bigsleep, Jan 25 2017
  

       I have so many [links] to add to this!
notexactly, Feb 26 2017
  

       Thanks, [notexactly], a lot to get my teeth into there.
nineteenthly, Feb 26 2017
  

       Notexactly, - your first link contains the sentence:
"This requirement for high light intensity means that lasers are required to study TPA phenomena."
Oh really?
Ian Tindale, Feb 27 2017
  
      
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