Playing DVD interfers with modem?

fred smith fredex at
Sat Feb 2 00:02:35 UTC 2008

On Fri, Feb 01, 2008 at 04:34:02PM -0500, Ric Moore wrote:
> On Fri, 2008-02-01 at 09:59 -0800, Rick Stevens wrote:
> > On Fri, 2008-02-01 at 00:19 -0500, Ric Moore wrote:
> > > When I play a video DVD the modem quits doing whatever it's doing.
> > > Strange. I'm running 32bit FC7 on a system with a 64bit AMD 3200 and 2
> > > gigs of memory. Both Xine and VLC exhibit the same behavior. I just
> > > tried gmplayer and it does the same thing, but the sound has static.
> > > That's weird, it never has before. Something else to fix. Sound on Xine
> > > or VLC is perfect. 
> > 
> > Uh, are the modem and the IDE port the DVD sharing an IRQ or something?
> > 
> > > So, how could playing a DVD foul up the modem? Is there some type of
> > > streaming to the network that could grab the serial line or the ppp
> > > session??
> > 
> > I can think of two things at least...the sharing of an IRQ or some other
> > hardware semaphore or simply the load put on the CPU by a soft modem.
> > However, with an AMD 3200, I don't think that's the issue.
> Lordy Rick, I'm an old BBS sysop from back when. I have a RS Robotics
> external with all the bells and whistles in hardware, so I'm connected
> only by a serial cable. I'm gonna check out your suggestion about the
> IRQ though. I sure miss setting pin jumpers. Devices generally stayed
> where you put 'em, IRQ wise. Here's /proc/interrupts

back 8 or 10 years ago I was having major trouble with my modem
(an external Micorcom 33.6). spent MUCH time trying to troubleshoot it.
in the end it boiled down to being interrupt priority. the serial port
I was using it on was NOT at the top of the priority list, so it kept
being serviced insufficiently often. Caused major havoc with all
serial comms. Found a package, somewhere, whose name I dont' remember,
that poked into the kernel and changed interrupt priorities. Putting that
serial port near the top of hte list solved the entire problem.

---- Fred Smith -- fredex at -----------------------------
               But God demonstrates his own love for us in this: 
                         While we were still sinners, 
                              Christ died for us.
------------------------------- Romans 5:8 (niv) ------------------------------
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