On Wed, Dec 11, 2002 at 12:35:24AM +0000, David Laight wrote:
> On Wed, Dec 11, 2002 at 11:10:06AM +1100, Daniel Carosone wrote:
> > On Tue, Dec 10, 2002 at 10:07:54AM -0800, Michael Graff wrote:
> > > If you get right down to it, so is copper.  There is a transmit pair
> > > and a receive pair.  It's the capabilities on each end that matter. 
> > 
> > I'm given to understand that this is not true for Gig-E on copper;
> > there's something smarter going on in the PHY's and they use all
> > wires for all signals.
> 
> IIRC it is the same as 100Base4, you transmit on 3 pairs
> and listen for collision on the 4th.

Nope.

http://www.mitech.co.uk/whitepapers/Insert-Guidance(Gigabit%20Eth).doc

"The 802.3ab task force selected Enhanced TX/T2 line code developed by
Level One communications for the implementation of Gigabit Ethernet,
this inherits the 100Base-T symbol rate and spectrum allowing auto
sensing 100/1000 products. 

The 1000Base-T achieves full duplex throughput by transmitting over each
of 4 pairs from both ends simultaneously. Each pair carries a dual
duplex 250Mbps data signal encoded as a 5 level pulse amplitude
modulation (PAM-5). "


1000Base-T does also support a half-duplex mode, but I don't know how
the signalling of collisions is handled.
 
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