From: Robert Harley
Subject: Re: Switching (was: Will Java VM kill Lisp? How to fight it.)
Date:
Message-ID: <5ii9i6$eaj@news-rocq.inria.fr>
······@netcom.com (Henry Baker) writes:
>·····@BellAtlantic.net wrote:
>>[...]
>>Computation is currently achieved by moving physical objects
>>from one place to another as a means of symbolizing information.
>>Moving these symbols around takes WORK [...]
>Of course this is complete hogwash. You won't find anything in any of
>your physics books that says that moving 'symbols' of 'information' requires
>WORK. [...]
Well the physics books on my planet say that decreasing the entropy of
a system by one bit dissipates k.T.ln 2 joules of energy as heat.
So if you want to have some hope of avoiding heat, you would need
perfectly reversible computations which, as I mentioned before, is not
a realistic prospect for the near future.
Henry, talk is cheap and waffling on about quanta is cheaper. If you
have some serious argument to put forward then go ahead. Otherwise
take it to alt.crackpots.
-- Rob.
From: Henry Baker
Subject: Re: Switching (was: Will Java VM kill Lisp? How to fight it.)
Date:
Message-ID: <hbaker-1004970823270001@10.0.2.1>
In article <··········@news-rocq.inria.fr>, ······@pauillac.inria.fr
(Robert Harley) wrote:
> Well the physics books on my planet say that decreasing the entropy of
> a system by one bit dissipates k.T.ln 2 joules of energy as heat.
>
> So if you want to have some hope of avoiding heat, you would need
> perfectly reversible computations which, as I mentioned before, is not
> a realistic prospect for the near future.
As readers of PhysComp Proceedings, etc., already know, even close
approximations to reversible computations help _a lot_. Suppose that a
'reversible' computation manages to dissipate 10% of its energy per bit
switched. This is still _ten times_ better than the 'non-reversible' gate,
which manages to dissipate 100% of its energy per bit switched.
While this may not be good enough for quantum computation, it sure beats the
heck out of boolean and/or logic.
From: Jeffrey S. Dutky
Subject: Re: Switching (was: Will Java VM kill Lisp? How to fight it.)
Date:
Message-ID: <334D0CF9.7132@BellAtlantic.net>
······@netcom.com (Henry Baker) writes:
>·····@BellAtlantic.net wrote:
> > [...]
> > Computation is currently achieved by moving physical objects
> > from one place to another as a means of symbolizing information.
> > Moving these symbols around takes WORK [...]
>
> Of course this is complete hogwash. You won't find anything in any
> of your physics books that says that moving 'symbols' of
> 'information' requires WORK. [...]
Clearly Mr. Baker is too busy to actually read my entire post. I did
not say that the " moving 'symbols' of 'information' requires WORK"
but rather that moving the physical objects that we use in all of
our computing machines to symbolize information requires work. The
actual post reads:
> Computation is currently achieved by moving physical objects
> from one place to another as a means of symbolizing information.
> Moving these symbols around takes WORK since the symbols are
> physical things (beads, cams, relay contacts, electrons) and
> that work generates heat due to friction (see the first and
> second laws of thermodynamics). The friction in a system can
> be minimized but not eliminated. Because information must
> by physically symbolized to be processed the production of
> heat by information processing devices is unavoidable.
Mr. Baker is clearly unwilling or unable to comprehend that while
the physical mechanisms with which we currently process information
are very small and fast they are still physical in nature. They have
mass and charge. They experience friction. Energy is required to
move them from place to place during the computation process. It is
this physicality that requires that computing produce heat.
In a more direct address to Mr. Baker's original post:
> The current assumption is that fast necessarily means 'hot' (in
> temperature and dissipation), although I can find nothing in my
> physics books that even remotely implies this connection. It's
> time to wipe the slate clean, and get some new ideas into this
> industry.
Mr. Baker is incorrect to characterize the connection between
speed and heat as an assumption. It is, rather, an observed fact
of all known implementations of computing machines. If Mr. Baker
is unable to find anything in his physics books to explain the
connection I can only conclude that it is a catastophic failure
of either Mr. Baker's physics books or of his own understanding.
- Jeff Dutky