Path: utzoo!attcan!uunet!husc6!bloom-beacon!apple!bionet!agate!helios.ee.lbl.gov!lll-tis!oodis01!uplherc!sp7040!obie!wsccs!terry
From: terry@wsccs.UUCP (Every system needs one)
Newsgroups: comp.dcom.modems
Subject: Re: UUCP g stats
Message-ID: <762@wsccs.UUCP>
Date: 3 Nov 88 05:19:23 GMT
References: <184@arnold.UUCP> <1892@van-bc.UUCP> <2032@udccvax1.acs.udel.EDU> <331@auspex.UUCP>
Lines: 37

In article <331@auspex.UUCP>, guy@auspex.UUCP (Guy Harris) writes:
> I write:
> >need for stop-bits.  While it is true that you still communicate to the
> >TrailBlazer or the HST asynchronusly, the actual connection is synchronus;
> >Timing is provided by a seperate clock, not the start and stop bits which
> >are needed to prevent framing errors in an asynchronus connection.
> 
> Umm, I think you missed his point.  The point is that you can't stuff
> data down the modem any faster than the serial port will allow; any
> extra bandwidth opened up by not using stop bits can't be spent sending
> data from the host, because the data isn't coming in fast enough.  It
> has to be spent sending error-correcting-code bits or something like
> that.

But the synchronus connection is what buys you such a high data rate in the
first place... the multi-carrier modulation used by Telebit requires it by
virtue of their encapsulation method.

The compression on the TB buys you exactly what you are saying it can't buy
you... putting characters in one modem and pulling them out another at a
higher rate than the modulation method used can push bits.

By incorporating compression encapsulation into a transfer protocol, and
using this protocol to transfer files, you CAN put more bits through the
serial port than the machine is capable of.  I STANDARDLY do this daily,
getting an average of 40% compression at 9600 between my DOS, my Xenix,
and the VMS and Ultrix machines I have access to.  My effective baud rate
is 9600 * 1.4 = 13340.  I have GOTTEN 95% on some graphics files.  You do
the math.


| Terry Lambert           UUCP: ...{ decvax, uunet } ...utah-cs!century!terry |
| @ Century Software        OR: ...utah-cs!uplherc!sp7040!obie!wsccs!terry    |
| SLC, Utah                                                                   |
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