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Date:      Thu, 5 Feb 1998 10:21:53 +0100 (MET)
From:      Thom Oostendorp <thom@mbfys.kun.nl>
To:        dwhite@resnet.uoregon.edu
Cc:        freebsd-questions@FreeBSD.ORG
Subject:   Re: modem - X problem
Message-ID:  <199802050921.KAA00216@antonius.mbfys.kun.nl>
In-Reply-To: <Pine.BSF.3.96.980204122558.15689F-100000@gdi.uoregon.edu> from "Doug White" at Feb 4, 98 12:26:23 pm

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Hello Doug White. You wrote:
> 
> On Wed, 4 Feb 1998, Thom Oostendorp wrote:
> 
> > I seem to have a weird problem when using a modem connection and X11
> > simultaniously.
> > 
> > Whenever I start a connection on my modem (it's on sio1) while X is running
> > X starts slurping up 50% of CPU time,and the system slows down
> > considerably. This happens for instance as soon as I start seyon, or
> > when ppp starts making an automatic connection.
> > As soon as seyon, ppp, or whatever stops using the modem, X drops
> > back to a modest few % of CPU time.
> 
> You don't have the modem and mouse set to the same port, do you?
> 

No, I'm not that stupid. The mouse is on sio0.

After some experimenting, if find that the combination of running X11 and
'cat /dev/ttyd1' is enough to cause the problem. 'top' shows that some 20% of
run time is spent on interupts, and some 40% by X11. 'cat /dev/ttyd1' without
X11 generates no interupts, and neither does X11 without 'cat /dev/ttyd1'.

Clearly, the interupts are the source of the slowness of the system. Where they
come from is a mistery to me; there is no data being recieved at that time.
I start suspecting a hardware problem, like some cross talk between the com1 and
com2 ports. However, in that case one would expect the same problems in Windows.

Thom

-- 
  Thom Oostendorp                    Dept. of Medical Physics and Biophysics
  thom@mbfys.kun.nl                  Geert Grooteplein 21   6525 EZ Nijmegen
  http://www.mbfys.kun.nl/~thom      University of Nijmegen, the Netherlands
  voice: +31 24 3614240              fax: +31 24 3541435
                                     buzzer: 06 65 325 533 (Netherlands only)



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