AUI crossover?

Paul Koning pkoning at
Tue Nov 1 15:59:53 CST 2005

>>>>> "Tony" == Tony Duell <ard at> writes:

 >> I am playing around with networking again, and realized I have a
 >> lot of AUI transcievers of different types, and only one AUI hub.
 >> Question is, can two AUI-male connecting converters be connected
 >> together with an appropriate cabelling, like you can do with
 >> RJ45/10bT, or must a person always use a hub/repeater box?

 Tony> No, AFAIK you need a repeater to handle the collisons, etc.

 Tony> I have a 2 port repeater somewhere (2 female AUI connectors to
 Tony> link to 2 transceivers), and it's remarkably complciated
 Tony> inside. There's a state machine type of thing with the state
 Tony> table in RAM, and a Z80 + ROM to boot that. Probably about 50
 Tony> chips all told.

Sounds like a DEREP, which I think is the first Ethernet repeater.
DEC box, roughly the size of the 3U routers of the time.

State machine with lots of discrete components sounds about right.
Z80 to boot it is puzzling, what is there to boot?  DEREPs were not
manageable, you just turn them on and they would work.


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