[svlug] How do I make a cross-over patch cable?

[Michael Higashi]

On Thu, 17 Sep 1998, Rafael Skodlar wrote:

> 100bT4 was invented for faster speeds and not to take advantage of low
> priced (and low quality) CAT 3 cable. If you check specs you'll find out
> that CAT 3 is not mentioned for higher speeds.

I guess you didn't look at the url Marc provided 
(http://wwwhost.ots.utexas.edu/ethernet/100quickref/ch12qr_4.html). 

The 100Base-T4 Quick Reference Guide does say you can use Cat 3, 4, or 5
cable, although Cat 5 is recommended. This is in accordance with what I
remember how Fast Ethernet was developed, T4 was created so people could
use their existing cable infrastructure.

100B-T4 uses one dedicated transmit pair, one dedicated receive pair, and
two bidirectional pairs. This means three pairs are sending 100mbs, so an
individual pair is carrying 33mbs. Yes, this stretches the bounds of what
Cat 3 is supposed to be able to carry, but that's the way it is.

Mike


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