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From: dopey@ihlpl.UUCP (James C Blasius)
Newsgroups: net.micro.att
Subject: Re: 7300 Probs. - CT are you out there?
Message-ID: <256@ihlpl.UUCP>
Date: Sat, 27-Jul-85 13:59:35 EDT
Article-I.D.: ihlpl.256
Posted: Sat Jul 27 13:59:35 1985
Date-Received: Mon, 29-Jul-85 06:22:05 EDT
References: <1054@homxa.UUCP>
Organization: AT&T Bell Laboratories
Lines: 32

> 	2) Why does the unixpc write to the screen so slowly when connected
> 	   to a host at 9600.  I have logged into a vax (thru cu) through an lan
> 	   (ungermann/bass) at 9600.  Still, characters appear on the screen
> 	   just as slowly as at 1200.  I have checked and it is not that the
> 	   vax is loaded down.
> 
I would suggest that if your terminal emulator on a 9600 baud line is
painting screens at a 1200 baud rate, something is broken in your machine!

seriously, I've just been trying my 9600 baud line to my 3b5 to see if
it paints at a 1200 baud rate and I assure you it's faster.  Nearly as fast
as a full screen vi session locally on the machine.

There is a misconception I've heard several dozen times concerning the
vt100 emulator.  The misconception is that the emulator runs slowly, even
at 1200 baud.  I would suggest that those of you who believe this try catting
large files with the emulator.  I think you will find that the emulator is
not slow.  The emulator is sporadic, not nearly as smooth in its screen
painting as cu for example, but it's not slow.

However, you must remember that the screen on the UNIX PC is a bitmapped
screen.  Bitmapped screens without special screen support hardware end up
making the processor move around large numbers of bytes whenever the screen
scrolls.  When you approach 9600 baud you may begin to find that your
overall throughput will not match the theoretical, more or less depending on
the kind of data you are sending (i.e., if you are sending short lines
there's going to be more bytes moved per character on average, etc).  This
is not limited to the UNIX PC, but is an issue with all bitmapped output
devices.

james blasius
ihnp4!ihlpl!dopey