The 1974 Bachrach Ethernet Memo

The Bachrach Ethernet Memo should have been long forgotten, but it has on the Internet taken on a life of its own, one that is impossible to delete. Altered versions of my 2008 eMail to Bytecoder Bill Heyman have proliferated with errors, so I am here posting the actual memo and will add related documents.

For whatever reason, the oft deleted sentence is: “I spent 30 minutes writing the memo and perhaps 2 hours in discussion with Bob and Dave. I then went back to the science on which I was focusing. Bob Metcalfe made Ethernet his life’s work and he is responsible for its successful adoption and spawning the revolution in computer communications.”

As an example, Reddit has an altered version archived and Zach into 2020 has a further altered version and labels it 2018. The blog is abandoned and who knows who is the blogger or how to contact him?

To: Bill Heyman ByteCoder Blog 2008
I am writing about your ByteCoder Blog entry “Xerox 1974: “[Ethernet] would be a failure” September 28 {link no longer active}
Since your Blog seems to be quoted and referenced quite frequently on this topic, I thought you should
understand the context and full situation.
I understand you were commenting out of context and certainly could not have understood the events or
circumstances. At the time I wrote my personal critique, Ethernet I had not been deployed within PARC and the
technical interaction about which you could not have known improved the deployed development prototype.
Below is a better recounting which I wrote after only recently learning that this private memo was floating around
and the subject of discussion.
Please remove the related blog posting
Robert Bachrach

Appropriately, through a conversation with Comedian Wayne Cutter ( ) about Xerox
PARC, I became aware in a Google search that my March 4, 1974 private Xerox Confidential Memo to Bob
Metcalfe and Dave Boggs concerning their draft paper on Ethernet-I was floating around the Internet and a major
subject on some blogs and even cited in Wikipedia. Unfortunately the role of my memo in the development of
Ethernet-II is not understood.
Ethernet was the invention of Bob Metcalfe and Dave Boggs as an outgrowth of Bob’s PhD thesis on the Aloha
Net packet communications network. As is well documented, Xerox PARC from the beginning (1972-1974) was
investigating distributed computing with the strategic intent to create an “Architecture of Information” in developing
the “Office of the Future”. Several communication technologies were in various stages of concept and feasibility
development when Ethernet-I was proposed. Ethernet-II at 3mbs emerged as the internal development vehicle
and Xerox commercialized Ethernet-III at 10mbs. Along the way to commercialization, a significant number of
PARC and Xerox staff contributed in addition to the inventors.
I joined the Xerox PARC General Sciences Laboratory from Bell Laboratories in the summer of 1973 where I had
worked on the first commercialization of light emitting diodes. At PARC our group was participating in the founding
of the Stanford Synchrotron Radiation Laboratory. Some of the prototype equipment we developed is now in the
Smithsonian Museum. Part of this equipment was an advanced computer aided data acquisition system I
developed. Although I am a condensed matter physicist, I was very interested in computers and software. I often
hung out with the guys in the Computer Science Lab (one of whom recently visited the space station) which is
how I received the first draft of Bob Metcalfe’s and Dave Bogg’s technical paper describing their Ethernet-I
networking concept. Ethernet-I described in the draft was a 3 mbs packet channel with software collision
Our practice at the time, as it was at Bell Labs, was to have open and frank critique and internal review of
technical papers before they were publicly released. It was in that spirit that I wrote my private memo which only
took on mythical proportions because CSL Lab Manager Bob Taylor chose to post it on his door labeled “Memo of
the Month”. The memo itself was written in 30 minutes at about 11pm the night before after I came home from
working in the lab.
CSL at that time was something of a “hippy commune” and meetings were held with everyone lying around on
bean bags. The first draft of the Ethernet-I paper was written accordingly in a hip style. At the time I considered
the draft quite an unprofessional document in addition to my technical concerns. I also at the time did not like the
idea of naming a major new networking innovation after a discredited physics concept, the “ether”. The ether
doesn’t exist and this was a real network on a real baseband coaxial cable medium. At the time of Ethernet-I,
packet collision identification was done in software with a CRC check of each packet. Software detection of
damaged packets would trigger staged random backoff until the valid packet was received.
Following the “memo”, Bob Metcalfe, Dave Boggs and I got together and had an extensive technical discussion of
their paper on Ethernet-I and its limitations. In that meeting I introduced them to the collision detection techniques
used in pulse counting apparatus such as I used in my photon counting spectroscopic equipment at Bells Labs
and at SSRL.1 Basically the receiver detection is an analogue to digital conversion and by suitable discrimination,
one can distinguish in hardware between one and two pulse events. If two packets collided on the Ethernet cable
at the transceiver, then the receiver could determine that the pulse signal was wrong and initiate correction.
The outcome of this discussion was Ethernet II. To my understanding, the Ethernet II hardware collision detection
incorporated into the transceiver resulted from this discussion and transformed the networking capability and
resolved many of the concerns I raised in my memo. Hardware collision detection was incorporated into the
transceiver. Hardware collision detection enabled an Ethernet-II communication channel to achieve effective
utilization while limiting the system overhead and paved the way for Ethernet’s future success as we know it today.
So to all the blogger’s out there, I was not a “Xerox Executive”, I was a young member of the technical staff , as
were Bob and Dave, contributing to the fertile discussion in a very creative multi-disciplinary lab. I have grown to
like the name Ethernet because of what has been accomplished. I don’t even mind all the other subsequent
packet communication techniques that call themselves XXX-Ethernet and aren’t. I spent 30 minutes writing the
memo and perhaps 2 hours in discussion with Bob and Dave. I then went back to the science on which I was
focusing. Bob Metcalfe made Ethernet his life’s work and he is responsible for its successful adoption and
spawning the revolution in computer communications.
So you network bloggers should now switch your attention to Liveboard, a PARC invention pioneered by John
Seeley Brown. Liveboard in the mid ‘80’s envisioned large flat panel interactive networked computer displays
which could be used for group meetings and networked meetings. Through my work at Applied Materials over the
last 17 years, we have created the ability to cost effectively manufacture such large LCD flat panel displays. LCDTV
and Computer Displays of 65”, 75”, and 108” are now entering mass production by our customers. Soon they
will be in homes, offices, class-rooms and enumerable public spaces. These Liveboard displays will now be
connected by Ethernet and also be lit by light emitting diodes whose commercialization I also helped pioneer.
Every time you look at your computer display, you are looking at technology I helped to create and enabled it’s
volume manufacturing.
In case you didn’t know. LCD displays are enabled by amorphous silicon transistors, another technology
pioneered at Xerox PARC in the 1970’s and commercialized by Applied Materials manufacturing equipment
starting in the 1990’s…
R.Z. Bachrach, Memorial Day Weekend, 2008.
1) R. Z. Bachrach, Rev. Sci. Inst., 43, 734 (1972), “A Photon Counting Apparatus for Kinetic and Spectral

3 Replies to “The 1974 Bachrach Ethernet Memo

  1. Thank you for another good write-up. Where else could anybody get that kind of info in such a ideal way of writing? Ive a presentation next week, and Im around the appear for these information and facts.

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