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From: gemini@homxb.UUCP (Rick Richardson)
Newsgroups: net.periphs,net.micro,net.wanted
Subject: Re: update on **real** 19200 CRT
Message-ID: <1842@homxb.UUCP>
Date: Fri, 1-Aug-86 11:23:56 EDT
Article-I.D.: homxb.1842
Posted: Fri Aug  1 11:23:56 1986
Date-Received: Sat, 2-Aug-86 23:10:27 EDT
References: <671@mordred.purdue.UUCP> <71@winfree.UUCP>
Organization: PC Research, Inc.
Lines: 32
Xref: mnetor net.periphs:490 net.micro:5738 net.wanted:3581

> All this talk about 19200 bu problems. (tisk, tisk)  I *KNOW* for a fact
> that IBM PC at 4.77 MHz using a standard CGA can emulate a full VT102 at
> 19200 baud.  I am doing it right now!!  I have measured the line, and
> sure enough, it is throughputting at 19200.  I use Mark Of The Unicorn's
> PC/InterComm program on the PC end, and a direct port to a DH unit on a
> VAX.  It will and does run 19200 baud.  The screen does not flicker, and
> you should even see Kermit zip along.  Anyway, EMACS, VI and even RN run
> perfectly fine; I have never had any of the problems.  The termcap that
> I use is the "dt80", with the SO and SE characters changed to show bright
> (the PC goes blue when it gets a \E[4h ); the termcap includes *NO* pad
> characters.  Note the the "dt80" termcap is identical to the "vt100-np"
> termcap without the initialization sequence for setting the tab stops.
> 					- bob
> Continuing Engineering Education Telecommunications
> Purdue University 		...!ihnp4!pur-ee!pc-ecn!sandersr

The talk is about 19200 *without ANY flow control*.  There is no way an
IBM PC can do 19200 *and* use software scrolling.  The scroll
operation takes much too long;  you have to be able to block move
4k bytes in <500usec or 122nsec/byte!  An 8088 takes ~2usec/byte.
Check this by sending *a long series newlines* and watch the line for
XON/XOFF or RTS/CTS handshaking.  If none occur, then PC/InterComm
is really doing 19200, and must be using hardware scroll.  Else,
it's just doing a good job with the average 19200 case, which is
not what the original poster was looking for.  Or, it's just trashing
some of the newlines, and you probably won't notice!  Better test:
send "a<newline> b<newline> c<newline> ..." repeated for several
minutes.  Watch the screen to make sure everything gets displayed,
and watch the line monitor for flow control.

Rick Richardson, PC Research, Inc. (201) 922-1134, (201) 834-1378 @ AT&T-CP
..!ihnp4!castor!{rer,pcrat!rer} <--Replies to here, not to homxb!gemini, please.