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From: lm@cottage.UUCP
Newsgroups: comp.arch,comp.sys.nsc.32k,comp.sys.intel,comp.sys.m68k
Subject: Re: Question:  on-chip or off-chip MMU?
Message-ID: <3608@spool.WISC.EDU>
Date: Wed, 20-May-87 16:19:04 EDT
Article-I.D.: spool.3608
Posted: Wed May 20 16:19:04 1987
Date-Received: Fri, 22-May-87 01:20:40 EDT
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Reply-To: lm@cottage.WISC.EDU (Larry McVoy)
Organization: U of Wisconsin CS Dept
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Xref: utgpu comp.arch:1256 comp.sys.nsc.32k:140 comp.sys.intel:228 comp.sys.m68k:460

I sez:
>>And this bit about optics?  Optics?  What will that buy you?  Sure light
>>travels fast but converting from electrons to photons is a drag.
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
(Adam Quantrill) sez:
#So why bother? Have optical sensors on keyboards, direct light output on
#your terminal screen. All comms can easily be optical fibre. No need to convert
#optical disk information into electrical current. The only reason
#for converting between electrons & photons is interfacing to the old electron-
#driven computers.
#       -Adam.
#
#/* If at first it don't compile, kludge, kludge again.*/

Because, my good sir, optical gates don't work very well yet.  And it looks
like they may never work very well.  In spite of what Sci America or any
other "knowledgeable" rag says, optical gates are more than likely pie
in the sky.  And until they or something else comes along, electrons and
computers will stick together.

    Now, optical busses are another question.  It's awfully nice to have 
a 64 bit bus in this teensy tiny fibre running across your chip.  Or acting
as a backplane bus.  But my original statement stands: conversion is a pain
and you want to look very carefully at the tradeoffs before embracing
optics.

Larry McVoy 	        lm@cottage.wisc.edu  or  uwvax!mcvoy