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Summary: Ethernet collision with modem?



Hi!

I got many responses for the question. Since some of them repeat each
other, and some others complement each other, it is useful to have a
summary, at least a temporary one, with some contributions of me.
Sorry for not mentioning everybody:

1. First of all, sorry for causing too much traffic on our list; I
   just followed up a question of Stas, regarding to Ethernet
   collision with modem (look at the title...) and didn't imagine
   that I would wake everybody up...
   BTW: Most of the Etherent cards use IRQ-10 or 11, so I guess that
   another thing caused the problem in the case of Stas.

2. To the people who asked why I couldn't do it through the Ethernet:
   This is the way I access my router currently, but I want an
   alternative way for an emergency case, when I am not near the
   router, and something got reset or damaged on it. I can dial up my
   server, but because of the problem, does not have any way to talk
   with the router. Note: I *can* access it serially, but only from
   my notebook, which is usually with me...

3. Choosing different IRQ: As almost everyone said, the best way is
   to use different IRQs. It can be done by changing the jumpers
   setting, which should be documented. Usually, IRQ of direct lines
   cannot be set, especially when the serial ports are on board.

   Anyway, the IRQ of the modem can be set, but only to some specific
   IRQs, usually 2, 3, 4, 5, and 7. Unfortunately, most of the PCs
   already use these IRQs. A typical map of a PC looks like:

   IRQ:   Use by:
   ====   =======
    1     Keyboard
    2     Programmable Stopper 
    3     COM4
    4     COM3
    5     Sound Blaster (I have a QIC02-tape on this IRQ)
    6     Floppy disk controller
    7     Paraller port
    8     Real Time Clock

   Of course, you still have to "tell" the software (or the operating
   system) that you changed the IRQ (look at /etc/rc.d/rc.serial and
   setserial(8) ). In some devices it requires you to change the
   source of the driver (as I had to do in my previous system, to
   solve the conflicts of the TPQIC02 tape).

   Since nothing should be changed in the settings of the direct
   lines, I don't have to explain how to change their "COM" number in
   the CMOS menus.

4. <plp@actcom.co.il> says that Linux can access devices which share
   the same IRQs. I can witness: In my previous system, I accessed
   both - IRQ02 tape and Sound-Blaster - through the same IRQ (5).
   There are some conditions, such as using the same bus (but not
   an ISA card with a PCI card), etc.

5. More tips: Doron <P85025@VM.BIU.AC.IL> recommends to use
   consecutive COMs (i.e. COM3 instead of COM4). He (pre-)said that
   although some of the things would work without it (as one of my
   previous systems), some others would not.
   Schlomo <schapiro@inter.net.il> recommends to prefer boards with
   PS/2 mouse port. My notebook has a PS/2 mouse port (in addition to
   the impossible-to-use built-in mouse), which allows me to use both
   - the modem and the serial port - concurrently. As I already said,
   The original question was not about this computer, but the server.

6. Re P.S.: Thanks to everybody who suggested me alternative ways to
   buy CDs from America. I know them, and could not use them because
   of some reasons. I didn't tell my story in order to get a
   solution, but only in order to help Stas. When talking about
   costs like 340 NIS, Stas 'is' so cheap, that you desire to tell
   him: "Stas, don't lower the price, increase it! We are with you!"

-- 
Eli Marmor
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