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full-duplex information in duxcw
biotch Oct-04-01 10:05 PM
On this page:
http://www.duxcw.com/digest/Howto/network/cable/cable5.htm

you state:

"Note that pins 4, 5, 7, and 8 and the blue and brown pairs are not used in
either standard. Quite contrary to what you may read elsewhere, these pins
and wires are not used or required to implement 100BASE-TX
duplexing--they are just plain wasted."

I presume this to mean "full-duplexing" in 100BASE-TX.

If so, what is the basis of this statement?
Several other references suggest a second tx/rx pair is necessary for full duplex ethernet.

Incidentally, the documentation for my 3com NIC, which supposedly supports full-duplex,
only shows pins 1,2,3, and 6 being used.

-bc


1. RE: full-duplex information in duxcw
lbyard Oct-05-01 04:47 AM
In response to message 0
The basis for the statement at the referenced page is fact. Two pairs are used for 100BASE-TX and 10BASE-T and two pairs in the cable are not used. One pair of wires connects to pins 1 and 2 and the other pair connects to pins 3 and 6. There are many erroneous documents on the Internet regarding networking. Some of them state the other two pairs are used to implement full-duplex when in fact there are two pairs and that is all that is needed to operate full duplex, if listening for packet collisions is not required in the network. If listening for collisions is required, the network will operate half-duplex. http://duxcw.com/faq/network/hubsw.htm. Larry

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