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Re: Slow booting with Intel EtherExpress Pro 100B



Actually my problem turned out to be some very dodgy ( please read very
early versions ) of a certain DEC21x4x based card.

Just wouldn't work back to back ! ( I suspect it was either some sort of
negotiation problem , or more likely an impedance matching problem on a
short cable run ).


BTW there is a reason for keeping the twisted pairs correct 
e.g. Orange/White & White/Orange is one pair ..

This is due to something called common mode rejection and is a fairly
standard technique for reducing interference. ( Both general noise &
between pairs ). If you mix and match conductors from different pairs -
you end up with a very distorted signal and a lot of collisions ).


Common mode means in effect "Signals Common to both conductors"
A twisted pair carries a differential signal and so if you subtract the
signal at the receiving end all you get ( in theory ) is the signal and
no noise !

( Tech mode cancel ! )

Andy.


Louis Abney wrote:
> 
> Back to back problems occured for me when I made my own cable and
> made the mistake of mixing the twisted pairs for receive and transmit.



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