Path: utzoo!attcan!uunet!mitel!sce!cognos!sysint!robert
From: robert@sysint.UUCP (Robert Nelson)
Newsgroups: comp.windows.ms
Subject: Re: Communication Error CE_OVERRUN under Windows
Message-ID: <250@sysint.UUCP>
Date: 9 Aug 89 03:28:44 GMT
References: <6755@cognos.UUCP>
Organization: Systems Interface Inc, Ottawa, Ontario, Canada
Lines: 58

chrisr@cognos.UUCP (Christine Roine) writes:

>Communication Problem
>---------------------

>One of our applications accesses and displays information retrieved 
>from a host computer via a serial communication line.  We have a
>communications bug that occurs fairly reliable, but cannot be
>reproduced with the same sequence of steps every time.  (Programmer's
>nightmare!)  The application runs perfectly for as much as 10 - 15
>minutes.  Then, suddenly, we get a CE_OVERRUN error returned by 
>GetCommError().  The documentation explains this as "A character
>is not read from the hardware before the next character arrives.
>The character is lost."  Our communication software asks for a 
>retransmission of the data that was lost, but CE_OVERRUNs keep 
>occurring in the retransmitted data.  

>At first we thought that perhaps we were writing over the interrupt vectors 
>in low memory.  However, a closer look at the data we were receiving
>revealed that we get some correct data after a CE_OVERRUN occurs.
>In some cases, for example, we are just dropping a couple of characters
>in the middle of a message.

[ Other descriptions of supposed causes and attempted solutions removed ... ]

>Has anyone run into this or a similar problem?

I believe that interrupts being disabled too long is your problem.  I don't
think that disk interrupts are the cause unless one or more of the following
are true:

	1)	your system is really slow

		(Nobody would use Windows on an XT :-) Would they??

	2)	you have a disk cache program which disables interrupts
		while transfering whole tracks

	3)	your disk controller is really slow

	4)	your disk sector interleave is wrong.

I have seen problems with the windows asynch driver when used with EMS
drivers.  If you are using one, try running windows with the /n option and
if that doesn't help try disabling the EMS driver in your config.sys file.

If the problem is with the EMS driver check with the vendor for a later
version or a fix.

>-- 
>Christine Roine          Cognos Incorporated     S-mail: P.O. Box 9707
>Voice: (613) 738-1440 x6111                              3755 Riverside Drive
>  FAX: (613) 738-0002                                    Ottawa, Ontario
> UUCP: decvax!utzoo!dciem!nrcaer!cognos!chrisr           CANADA  K1G 3Z4
-- 
Robert B. Nelson                               Systems Interface Inc.
Phone: (613) 727-5001                          223 Colonnade Road South
UUCP: uunet!mitel!sce!cognos!sysint!robert     Nepean, Ontario, CANADA, K2E 7K3