[SGVLUG] Cable ethernet problems

[matti]

hmmm... 10baseT and 100baseT 
i thought you still needed both pairs
TX (transmit) and RX (receive)

with half duplex it would only be transmitting
on one pair at a time

references
http://en.wikipedia.org/wiki/Full-duplex_Ethernet
http://en.wikipedia.org/wiki/10BASE-T
http://en.wikipedia.org/wiki/Duplex_(telecommunications)

best
matti



--- On Wed, 12/24/08, David Lawyer <dave at lafn.org> wrote:

> From: David Lawyer <dave at lafn.org>
> Subject: Re: [SGVLUG] Cable ethernet problems
> To: "SGVLUG Discussion List." <sgvlug at sgvlug.net>
> Date: Wednesday, December 24, 2008, 7:00 PM
> > 
> > hi,
> > 
> > >.. I'm
> > > connecting it to a laptop running Windows XP. 
> Does it take
> > > a
> > > straight-thru cable or a crossover cable? 
> > 
> > 
> On Mon, Dec 22, 2008 at 03:46:49PM -0800, matti wrote:
> > [PC/NIC]----[PC/NIC] = need a cross over cable.
> 
> I thought that the reason for this was so that one could
> use full
> duplex.  But it's claimed that my NIC is only
> half-duplex where the
> same channel is presumably used for transmit and receive. 
> Since the
> crossover cable provides two pairs between pins 1-2 and 3-6
> then is
> only one of these pairs used?  If so, how does one side
> know if they
> should use 1-2 or 3-6.  It can't be negotiated since on
> this old card
> there are likely no provisions for negotiation like there
> are for modern
> cards.
> 			David Lawyer