ethernet patch cables

[Lennart Sorensen]

On Wed, Jan 30, 2008 at 11:00:29AM -0500, Lennart Sorensen wrote:
> Isn't that what most machines with gigabit use?  Well actually
> 1000Base-T (never heard of 1000Base-TX).  It can run on Cat5 but only
> properly installed cat5 that hasn't been abused.
> 
> 1000Base-T does put more demand on the cable than 100Base-TX since
> 100Base-TX runs 125MHz signal with a 5:4 encoding of the data to get
> 100Mbit, and hence has some error correcting and detecting ability and
> runs traffic one way only on a single pair per direction.  1000Base-T
> runs 125MHz signal with data on both high and low clock (so 250MBit on a
> single pair) which looses the error correction and detection ability of
> 100Base-TX and it transmits and receives on all 4 pairs of wires at the
> same time, so it has to deal with interference that may occour as well
> as keeping the transmitted and received data seperate even though it
> shares the wire and it has to deal with cross talk from 4 active pairs
> rather than 2.  Since the actual frequency of the signal is still 125MHz
> just like 100Base-TX the cable should be OK, but the reduced protection
> against errors and the increased number of pairs carrying data puts
> higher demand on a good quality cable.

Turns out I had missed something when I looked up gig ethernet in the
past.  It does have some error detection through the use of multiple
voltage levels for signaling.  It is more complex than 100Mbit though
and it does use all the wires at the same time.

--
Len SOrensen
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