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From: hindmost@mit-trillian.MIT.EDU (Brian R. Murphy)
Newsgroups: net.micro.cbm
Subject: Re: 2400 baud modems
Message-ID: <980@mit-trillian.MIT.EDU>
Date: Sun, 10-Aug-86 06:51:30 EDT
Article-I.D.: mit-tril.980
Posted: Sun Aug 10 06:51:30 1986
Date-Received: Mon, 11-Aug-86 04:56:21 EDT
References: <2050@watmath.UUCP> <865@usl.UUCP>
Reply-To: hindmost@trillian.UUCP (Brian R. Murphy)
Organization: MIT Project Athena
Lines: 38
Keywords: terminal emulators

In article <865@usl.UUCP> elg@usl.UUCP (Eric Lee Green) writes:
>In article <2050@watmath.UUCP> grwalter@watmath.UUCP (Fred Walter) writes:
>>Query: has anyone had any experience using a 2400 baud modem with a C64
>>or a C128 ? Can either of these computers support 2400 baud, even in
>
>2400 baud is impossible on a C-64, unless you totally chunk all Kernal
>routines (in which case it would STILL be extremely unreliable, and
>you would be limited to 40 columns because 80-column emulation is too
>slow even for 1200 baud).

I don't think you'd be limited to 40-columns.  The 80-column screen
does slow it down (I can't remember how much cpu it steals right now,
but a terminal emulator I wrote using kernal routines never made it
past 600 baud or so with software 80-columns), but not that much.
I took a look at the routines, and they seemed to leave much room
for improvement, so with your own it seems like you could do it.
If anyone already has these, it would be nice if you'd post them.

>Commodore personel have stated that 2400 baud is possible on a C-128
>while running in 80 column mode at 2Mhz. I am not qualified to judge
>the truthfulness of this statement, since I do not have a 2400 baud
>modem and have only had a C-128 for 3 weeks. It does seem rational,
>though... processor twice as fast, baud rate twice as fast, and with
>the 128's real 80 column screen, no problem emulating a "smart"
>terminal.

2400 baud does work on the 128; I converted a terminal emulator I wrote,
using standard kernal rs-232 routines, on the 64 with few problems
recently.  It seemed unreliable at 1mhz and 2400 baud, even using the
nice hardware scrolling in the VDC (really burns compared to anything
without it), but at 2mhz it works perfectly, with an Anchor 2400 baud
modem (which I've had no problems with).  I'm working on a vt-220
emulator now, and I hope I can get it faster than 2400 baud using
custom low-level i/o.  Any suggestions?

-Brian Murphy
hindmost@athena.mit.edu
{ decvax!genrad, ihnp4 }!mit-eddie!mit-athena!hindmost