[svlug] help transfering data over 1394 cable

[Rick Moen]

Quoting Daniel Gimpelevich (daniel at gimpelevich.san-francisco.ca.us):

> Data may only travel on a crossover cable in one direction at a time
> ("Half Duplex"),

No, that's not the case.  Reference:  
http://en.wikipedia.org/wiki/Crossover_cable  
 
> Additionally, the wiring standard for crossover cables is incompatible
> with the Gigabit Ethernet specification, causing it to fall back to 100Mb.

A _proper_ 1000BASE-T4 crossover cable that crosses all four pairs does
support gigabit easily.  You can even squeeze by with CAT5 cabling if
(like me) you still have too much of that sitting around, and are cheap,
and use short lengths, and aren't creating long-term solutions -- albeit
the official spec requires at worst CAT5e.  Here's the pinout diagram
(figure labelled "Gigabit crossover"):
http://en.wikipedia.org/wiki/Ethernet_crossover_cable

I've been guilty of making two-pair crossover cables in the past, per
the TIA/EIA T568A or T568B spec, but have cured that bad habit lately.
You're right that two-pair crossover cables definitely would not do the
trick.

> Also, many Ethernet ports today will automatically crossover
> a regular Ethernet cable correctly at the correct speed anyway.

Yes, this is the MDI/MDI-X autosensing aka "unversal cable recognition"
that I spoke of earlier, and is why you always try a straight-through
cable _first_ before shelling out for (or even reaching for) a crossover
cable.