Path: utzoo!utgpu!news-server.csri.toronto.edu!helios.physics.utoronto.ca!ria!uwovax.uwo.ca!baer
From: baer@uwovax.uwo.ca
Newsgroups: comp.windows.ms
Subject: Windows handling multi-tasking with comm. pgms.
Message-ID: <1991Jun27.232646.9501@uwovax.uwo.ca>
Date: 28 Jun 91 04:26:46 GMT
Lines: 39


I am running a communications app. which comes in both a DOS and an OS/2
version (Rexxterm).  I just purchased a 9600 baud modem for my 16mHz
386sx.  This modem has MNP 5 (and v.42) error correction; of these 2,
the modem at the "mainframe" end seems to provide MNP 5 but not v.42.
MNP 5 should provide a throughput of up to 19,200 baud.  Under Windows 3,
when I run the serial port at 19,200 baud and connect at 9600 baud,
I lose characters, even with the communications app. running in the
foreground and no major app's running in the background (file system,
pgm. manager that's all).  With the serial port set at 9600 baud, 
I have no problem with the comm. program in the foreground.  With any
serious multi-tasking in 386 enhanced mode, even this configuration 
(9600 serial port speed) isn't low enough: there is a loss of characters
when I run the com. program in the background (priority=100) and
either Word Perfect or a stats program in the foreground (priority=100).
This despite the fact that the foreground program suffers some 
degradation (typed characters take a while to appear on screen etc.).

Under DOS alone, there is no problem running the communications 
program with the serial port set at 19,200 baud.

Under OS/2, there is no problem either, even when I have 2 or 3 
other processes running.  I can run a stats program in the background
and WP for OS/2 in the foreground (or vice versa), with the comm.
program in the background transferring files with a serial port
speed of 19,200 and no characters are lost (although as I load
more foreground processes, the actual transfer rate seems to go down
-- there must be some handshaking going on -- OS/2 seems to be able
to keep up with my modem when data are shovelled through).

Just thought you might be interested.  Technical explanations/discussions
invited.   


-- 
---------------------------------------------------------------------
Douglas Baer, 
University of Western Ontario, London, Canada N6A 5C2
Internet: BAER@UWO.CA    Bitnet: BAER@UWOVAX