3Mb Ethernet

From: Brian Chase <bdc_at_world.std.com>
Date: Sun Apr 22 14:54:44 2001

On Sun, 22 Apr 2001, ajp166 wrote:
> From: Tony Duell <ard_at_p850ug1.demon.co.uk>

> > AFAIK it is not backwards-compatible, at least in the sense that no
> > 10Mbps ethernet controller supports the 3Mbps data rate (at least, I've
> > never seen one that does).
>
>
> Neither have I. Also Eithernet AKA 802.x was never that slow. The
> 3 mb/s stuff I'd always called ARCNET.

No, ARCNET is a different beast. The original implementation of Ethernet
at Xerox PARC on the Altos systems ran at 3Mbps. ACM has a webified
version of the 1976 paper "Ethernet: Distributed Packet Switching for
Local Computer Networks" by Robert M. Metcalf and David R. Boggs.

  http://www.acm.org/classics/apr96/

Under section 4 of the paper, it is explained that 3Mbps was used because
of the nature of their minicomputers. Some other sources around the web
say that the first implementation done at PARC was done in 1973. My guess
is that around that time, most minicomputers wouldn't be able to deal very
well with a firehose of data streaming in at 10Mbps.

The IEEE 802.3 standard didn't come about until a number of years later.

-brian.
Received on Sun Apr 22 2001 - 14:54:44 BST

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