Re: apple IIGS

[CUTjefbla@bconnex.net (Jeff Blakeney)]

On Fri, 1 Jan 1999 16:26:46 +1300, dempson@actrix.gen.nz (David
Empson) wrote:

>Jeff Blakeney <CUTjefbla@bconnex.net> wrote:
>
>> 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.

I'm confused now.  How does sending less data transfer into wasting
transmission time?

If it takes say 12 seconds to transfer some uncompressed data and only
3 seconds to transfer the compressed data, even allowing for a extra
time for the modem to check the file to see if it can be compressed
and actually do the compression (which is usuaully done in hardware
and happens very quickly), it still is going to be transmitted in much
less than 12 seconds.

>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.

Yes, you still do get some compression but you won't get as good of
compression as you do without the TCP/IP packet system.

And again, it depends on what you are transferring.  If you are using
a graphical web browser to view a web page you would get some
compression for the HTML file but would get practically none for the
graphics so overall the web page would be transferred in almost the
same amount of time with compression on as it would with compression
off.

However, if you are primarily transferring text then, yes, you'll
probably still want to keep compression turned on.  You won't get up
to the maximum of four times compression but you will still get some
compression.

The point I was trying to get across (which I admit I did a pathetic
job of doing :-) is that you don't need to worry about losing too much
transfer speed if you put a 28.8kbps, 33.6kbps or 56kbps modem on your
IIgs if you are primarily going to be doing TCP/IP stuff.  You may
only be able to set your serial port to 57.6kbps so you can't get the
full compression but you don't lose as much transfer rate if you are
doing TCP/IP.

This explanation still looks pretty pathetic but I've spent too much
time typing this message as it is so I'll let it go and do damage
control later.  :-)

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    Jeff Blakeney - Dean of the Apple II University on Delphi
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