Newsgroups: comp.windows.ms
Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!caen!ox.com!math.fu-berlin.de!fauern!faui43.informatik.uni-erlangen.de!testurm
From: testurm@immd4.informatik.uni-erlangen.de (Torsten Sturm)
Subject: Re: Windows handling multi-tasking with comm. pgms.
Message-ID: <1991Jun28.161908.681@informatik.uni-erlangen.de>
Organization: CSD., University of Erlangen, Germany
References: <1991Jun27.232646.9501@uwovax.uwo.ca>
Date: Fri, 28 Jun 1991 16:19:08 GMT
Lines: 26


Hi, I'm working on a DDK-Driver, so I have the source code of
the comm.drv driver.
The thing is, that this driver is not sending and receiving
an array of characters on an interrupt-based way !! (BTW the assembler
code written there is a terrible one, i've not expected that from MS).
If you send a buffer of chars to the commport, you call WriteComm(..),
which (and now listen good) make a while loop, calling for each char
a routine named $SNDCOMM, not like a normal commdriver with an inter-
rupt scheme !!

So the best speed you can expect is 9600, if you are lucky.

In 386-Mode, the is additionally a vitual device driver between the 
port and the windows comm.drv, which handles the intterupts !
So it could be even slower than in 286-mode !

That all is common weakness of Windows !
Hope that helps !!
---
Torsten Sturm 
tnsturm@faui09.informatik.uni-erlangen.de
tnsturm@faui40.informatik.uni-erlangen.de
testurm@faui41.informatik.uni-erlangen.de
testurm@faui43.informatik.uni-erlangen.de
storm@faui80.informatik.uni-erlangen.de