Re: OT: Four leads = 10Mbit? (was: Network speed)

[Richard Hector <rhector@paradise.net.nz>]

On Thu, Jul 24, 2003 at 11:50:48AM -0300, breno.moiana@partekforest.com wrote:
> 
> I?ve noticed that some of the most recent 100Mbit cards I've been buying (Genius
> low end cards, model GF100TXR4) have only four connection points on the RJ45
> slot. However, the cards *do* work at 100Mbits. Anybody with the technical
> knowledge on the subject could please explain that? Why do 3Coms have all 8
> leads, while low-end use only 4? how does it affect the quality of connection?
> Are all 8 leads really used?

Only 4 wires (better to think of it as 2 pairs) are used, but I believe the
better cards ground the others (or maybe just connect a resistor across each
pair), so you don't get stray signals bouncing up and down the others, which
you might if they were open ended. That could possibly cause crosstalk, and
hence noise on the used pairs.

But then I failed telecommunications theory, so someone else could probably
explain it better ...

Richard