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From: gareth@comp.lancs.ac.uk (Gareth Husk)
Newsgroups: comp.arch
Subject: Re: Optical Computing (Not optical communications)
Message-ID: <352@dcl-csvax.comp.lancs.ac.uk>
Date: Fri, 1-May-87 06:31:31 EDT
Article-I.D.: dcl-csva.352
Posted: Fri May  1 06:31:31 1987
Date-Received: Sun, 3-May-87 04:01:25 EDT
References: <3560@cbosgd.ATT.COM> <2547@dalcs.UUCP>
Reply-To: gareth@comp.lancs.ac.uk (Gareth Husk)
Organization: Department of Computing at Lancaster University, UK.
Lines: 38

In article <2547@dalcs.UUCP> thompson@dalcs.UUCP (Michael A. Thompson) writes:
>
>	Two or three years ago, I read a article in Scientific
>    American (I don't remember the exact issue but if anyone is
>    interested I can look it up) about these optical transistors that
>    someone had developed. The thing that impressed me is that not
>    only would you get the high speed of light in a computer built of
>    these things but you could also get parallel computing by using
>    different colors of light.
>-- 

The edition of SciAm was December 198[12]. The group that developed
these wee beasties is based at Heriot-Watt University in Edinburgh.

I went to a talk by one of the group last year and he was a bit 
embarrassed by the article. He said it represented an awful lot
of crystal ball gazing. And that the editors had removed the
depressing stuff about what they actually had working rather than
what *might* happen.

What they have got are discrete components cooled by liquid Nitrogen
and they are using a thermal effect in the switching, thus the speed
of switching is v.low because they have to wait for the device to 
stabalise after each switching. So that although transmission is
~.9c switching is governed by fairly low speed thermodynamic effects.

Dr. Abrahamson (sp) was talking of 15-20 yrs more work at least plus
the need to have optically reactive materials or much smaller thermal
effects to lift processing speeds to the pico second levels mentioned
in the article.



-- 
" I am a doughnut "  JFK

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