[SGVLUG] Cable ethernet problems

[David Lawyer]

I'm having trouble getting ethernet to work using an ISA card from
1994 that supports both coax cable (2 types) and twisted-pair.  It's a
3com 3c509.  According to the driver doc. it is only half duplex.  I'm
connecting it to a laptop running Windows XP.  Does it take a
straight-thru cable or a crossover cable?  I set the Windows driver
for half-duplex and the Linux driver has been recently changed so that
it can't be set by options for full or half duplex.  So I would expect
it to require a straight-thru cable since it should only use one pair
of wires ??  But the green light on both cards only comes on when I use
a crossover cable.  Windows says it's connected, but while both
computers send packets, none are received by the other side and no
interrupts in Linux are sent.

But I've never used this NIC card (ISA bus)  before and got it with a
used PC, so it might not work correctly.  The speed is 10Mbps and
Windows has been told this, so it shouldn't be a speed mismatch.  How
do I troubleshoot this?  How does half-duplex work over a crossover
line with 2 circuits.  Does each of the twisted pairs have
bi-directional flow on them with collisions (half-duplex)?

I suspect that something may be wrong with the linux driver module.
For one, the instructions are wrong since the change log says the
option of telling the driver whether it's half duplex, or whether it's coax
ethernet (which I'm not using) has been removed.  But this option is
still mentioned in the kernel documentation.  The instruction manual
for the old ethernet card says that by default it works for coax cable
and you need to use windows software to change it to twisted pair if
that's what you're using.  But since the Linux driver used to permit
you to specify twisted pair, apparently this driver can set up the
card to use twisted pair.  Perhaps the driver sets it to twisted pair
in all cases and has disabled the provision of the card to use coax.


			David Lawyer