Wanted: PDP-11 Unibus Ethernet interface from Xerox, c. 1981

Rich Alderson RichA at LivingComputerMuseum.org
Tue Mar 31 14:11:53 CDT 2015

From: Noel Chiappa
Sent: Tuesday, March 31, 2015 6:19 AM

> If this is the card I'm thinking of (we got two as part of the Xerox donation
> of Altos, a Dover, etc to MIT, BITD), it's to a 3-MBit Experimental Ethernet,
> not to a 10-MBit Ethernet, and so won't be much use unless you have something
> else with a 3-MBit Ethernet (and of course you'd also need 3-MBit
> transceivers, etc, etc).

I've been given further information from my WAITS advisory team.  This is
indeed the card you're thinking of.  Like MIT and CMU, Stanford got a donation
of a Dover printer, lots of Altos, and the 3Mbit card for the PDP-11.  Stanford
put theirs into SAIL and made WAITS talk to the Ethernet through the front end.

When I went to work at Stanford LOTS in October, 1984, the campus network was
still primarily 3Mbit PUP.  I installed a 10Mbit MEIS into one of our DEC-20s
as part of the beta for the updated monitor code sometime after that.

> And of courset those cards were made in very, very limited numbers; if any
> survive to this day, I will be absolutely astonished.

So will I, but I have to ask.

> If you have a pointer to the PDP-11 code, I can take a look at it and confirm
> if it's a 3-MBit card. (The hardware packet header format is completely
> different from that for a 10-MBit.)

This has only just come up in the last 36 hours, so I don't have my hands on
the code in question yet, but the rest of the evidence says that we don't need
this corroboration.


Rich Alderson
Vintage Computing Sr. Systems Engineer
Living Computer Museum
2245 1st Avenue S
Seattle, WA 98134

mailto:RichA at LivingComputerMuseum.org


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