AUI crossover?

[der Mouse]

> You missed the Collision wires, and therein lies the trouble.

> There are two issues. 

> One is that an AUI based Ethernet was half duplex (just like
> 10Base2).

It's not entirely fair to contrast AUI and 10base2 this way, as if they
were comparable things.  AUI is the interface between the host and the
transceiver; 10base2 is one of various possibilities for the medium on
the other side of the transceiver.  Contrasting AUI with 10base2 is a
bit like contrasting RS-232C with POTS phone service (just as the one
applies to different sides of a transceiver, the other applies to
different sides of a modem).

> The other issue is that 8u02.3 compliant NICs will expect the
> collision signal to assert briefly after each packet.  That is the
> Collision Test (SQE test, see 802.3 section 8.2.2.2.4).

Some will.  Many don't care.  I think I have even seen a few that
object if they *do* get that signal.  I have some transceivers which
have switchable SQE and have done a little experimenting....

> You said you have lots of transceivers.  So why do you want
> crossover?  Just hook the AUIs to their coax and wire up a classic
> Ethernet that way.

Perhaps there's no co-ax at ready hand?  If the transceivers use
10base5 this seems reasonably likely.

> (For that matter, what's an "AUI Hub"?  I know AUI repeaters, and I
> know AUI transceivers.)

In my experience, the term is used colloquially to refer to an AUI
multiport transceiver box, especially one that is capable of running
without a real transceiver attached.  (A multiport transceiver is a
device that has multiple - typically 8 - AUI connections suitable for
connecting to hosts and one AUI connection suitable for connecting to a
real transceiver.  As far as the hosts are concerned it looks like
multiple transceivers on the same medium.  Some of them demand having a
real transceiver on the transceiver port; some have a switch that lets
them run without, and some of the newest auto-sense.)

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