Re: apple IIGS

[dempson@actrix.gen.nz (David Empson)]

Jeff Blakeney <CUTjefbla@bconnex.net> wrote:

> On Thu, 24 Dec 1998 21:14:23 -0700, Frank Carney
> <frankcNOSPAM@cyberhighway.net> wrote:
> 
> >Where do you get the idea that a modem is anything other than a serial
> >connection?  I does have buffers, and it can compress the data in the
> >buffer before it is sent, but to the computer it looks identical to what
> >was sent.  There is no way the file is going to get larger.  It may have
> >transferred slower before and maybe the compression routines were slow,
> >but the information goes in one side and is the same on the other side.
> >Think about it, it is just a serial port to the program using the modem
> >after you have connected.
> 
> Modem compression schemes before MNP 5 would increase the size of an
> already compressed file.

Yes, fine.  But they only did this for the transmission of the file -
what comes out the other side would be exactly what went in at the
sending end.  It just wastes transmission time.

That was Frank's point.

> By the way, because of the way TCP/IP works, turning on compression in
> your modem while using TCP/IP, you will not see the 4 times
> compression of text files.  TCP/IP splits data up into "packets" which
> breaks up the repetition and such so data cannot be compressed very
> much so there will be little improvement with having compression
> turned on.  Just something to think about now that we have TCP/IP for
> the Apple IIgs.

I disagree.  The data may be broken up into packets, but there is still
enough localised repetition for V.42bis to get a fair amount of
compression.

I tried disabling compression on my modem once and got significantly
worse performance when transferring text files.

-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand