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241 lines
9.1 KiB
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<TITLE>The Answer Guy 37: X Prevents/Kills Modem Connection</TITLE>
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<H4>"The Linux Gazette...<I>making Linux just a little more fun!</I>"</H4>
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<H1><A NAME="answer">
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border="0" align="middle">
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<font color="#B03060">The Answer Guy</font>
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</A></H1>
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<BR>
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<H4>By James T. Dennis,
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<a href="mailto:linux-questions-only@ssc.com">linux-questions-only@ssc.com</a><BR>
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Starshine Technical Services,
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<A HREF="http://www.starshine.org/">http://www.starshine.org/</A>
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</H4>
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</center>
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<H3 align="left"><img src="../../gx/dennis/qbubble.gif"
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height="50" width="60" alt="(?) " border="0"
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>X Prevents/Kills Modem Connection</H3>
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<p><strong>From ktoyama on Thu, 14 Jan 1999
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</strong></p>
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<!-- ::
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X Prevents/Kills Modem Connection
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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:: -->
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<P><STRONG><IMG SRC="../../gx/dennis/qbub.gif" ALT="(?)"
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HEIGHT="28" WIDTH="50" BORDER="0"
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>
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Dear Answer Guy,
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</STRONG></P>
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<P><STRONG>
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Great forum of Q&A here at the Linux Gazette. Here is my problem.
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</STRONG></P>
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<P><STRONG>
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I'm trying to use a US Robotics 28.8 (no winmodem) and it works fine
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under the linux console under windows 1-6. Once I start-up X it doesn't
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seem to connect to the modem and seems to lose the connection to the
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modem. I start up the pppd which invokes the chat script but the modem
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never does a connect. But if I quickly switch to (CTRL-ALT-F1) or and
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F1-F6 window, the modem will dial and connect. Then I switch back to X
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and there is a connection. I can check mail, view web pages, but then
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after about 2 minutes everything stalls and the connection is lost. If
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I switch to a console for 15-20 seconds the link restores it's speed and
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then I can switch back to X. Then the cycle starts all over again.
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Please help me in determining the root of the problem. Thanks.
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</STRONG></P>
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<P><STRONG>
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Sincerely,
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</STRONG></P>
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<P><STRONG>
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Kevin
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</STRONG></P>
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<BLOCKQUOTE><IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
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HEIGHT="28" WIDTH="50" BORDER="0"
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>
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My first guess would be that you have an IRQ problem.
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If you modem and your mouse are trying to use the same
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IRQ --- and your modem is inactively while you're at your
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text consoles (i.e. you're not using gpm) --- that would
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be the most likely problem.
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</BLOCKQUOTE>
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<BLOCKQUOTE>
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Other problems are possible. Some video cards use IRQ
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2/9 (daisy chained IRQ pair) which might cause conflicts
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while you were in graphics mode, while not causing any
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problem from text consoles.
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</BLOCKQUOTE>
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<BLOCKQUOTE>
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Yet another problem might have to do with the system's
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overall computing power. If you have a high speed
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modem connection it could be that X takes enough of
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your CPU horse power that the serial driver gets
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starved for attention (although that would also
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suggest flow control problems).
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</BLOCKQUOTE>
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<BLOCKQUOTE>
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Of course a 28.8 and any sort of Pentium (even a P60)
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should be reasonably well matched --- assuming you have
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enough RAM that you aren't thrashing to disk.
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</BLOCKQUOTE>
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<BLOCKQUOTE>
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Does this only happen with PPP? What if you connect
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to a BBS (or dial-up shell), start a file transfer
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and then start X? If the transfer (zmodem, Kermit,
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or whatever) still runs smoothly for several minutes
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after switching to X --- it suggests some sort of
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networking problem. If not, try running a file
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transfer while starting a non-X graphics program
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(such as 'zgv' --- the SVGAlib .GIF and JPEG viewer).
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</BLOCKQUOTE>
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<BLOCKQUOTE>
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Also try running a file transfer while performing
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"cut and paste" operations on your text mode VCs
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(run 'gpm' to do that). Transfer a couple of page
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fulls of a man page into an empty editor session
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('vi' -- 'emacs' or whatever).
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</BLOCKQUOTE>
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<BLOCKQUOTE>
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As with any problems with any daemons, look in your
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<TT>/var/log/messages.</TT> Are there any error messages being
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posted through the syslog subsystem? Try increasing the
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debugging output of your pppd by adding the debug and
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kdebug directives to your <TT>/etc/ppp/options</TT> file (as per
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the man pages).
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</BLOCKQUOTE>
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<BLOCKQUOTE>
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Try posting the contents of your PPP options file(s)
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and the command that's being used to invoke it (which
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may over-ride many of the directives in the options
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file by listing conflicting options on its command line
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or pointing to a supplemental options file using the "file"
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directive).
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</BLOCKQUOTE>
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<BLOCKQUOTE>
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Try a different video card and/or a different X server.
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(You could even try starting a "monochrome" X server).
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</BLOCKQUOTE>
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<BLOCKQUOTE>
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It's also possible that the problem lies with some
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X application or "toy" ('clock', your window manager, etc)
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rather than with the X server itself. If the probably
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recurs while running 'zgv' or some other SVGAlib program
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--- then you can conclude that it has more to do with
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the hardware/drivers than with the applications.
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</BLOCKQUOTE>
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<BLOCKQUOTE>
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With any troubleshooting process you want to try all sorts
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of things that help isolate the exact components (hardware
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and software) that are involved. Many of these tests may
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not be usable as "work arounds" but they can define the
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problem more precisely.
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</BLOCKQUOTE>
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<BLOCKQUOTE>
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You can browse around under the <TT>/proc</TT> filesystem to
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find out a bit more about which IRQs are in use and you can
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use the 'procinfo' and similar commands to determin more.
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</BLOCKQUOTE>
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<BLOCKQUOTE>
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(If this is a laptop running PCMCIA drivers -- for example
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--- then there are any other potential problems, as
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laptop hardware tends to be very quirky --- video and
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PCMCIA interfaces especially).
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</BLOCKQUOTE>
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<!-- sig -->
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<!-- end 30 -->
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<P> <hr> <P>
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<H5 align="center"><a href="http://www.linuxgazette.com/copying.html"
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>Copyright ©</a> 1999, James T. Dennis
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<BR>Published in <I>The Linux Gazette</I> Issue 37 February 1999</H5>
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