Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!ncar!boulder!daemon
From: BILLW@mathom.cisco.com (WilliamChops Westfield)
Newsgroups: comp.dcom.sys.cisco
Subject: Re: strange behaviour involving repeaters
Message-ID: <23193@boulder.Colorado.EDU>
Date: 6 Jul 90 23:49:44 GMT
Sender: daemon@boulder.Colorado.EDU
Lines: 26

Ok, here is the complete story.

In early 1989, a batch of MCI boards were built with an incorrect TYPE
of crystal.  This incorrect crystal caused the wire clocking to run
.03% faster than 10 Mhz.  The Ethernet Spec only allows .01% variation,
so we were 3x over the variation limit (Which is not nearly the same
thing as being 3x too fast!)  In most cases, the interfaces continued
to work just fine, and interoperated with all other devices on the
ethernet cable.  However, some devices, notably some twisted pair
ethernet transceivers, didn't like it.  Most of the MCIs that were
causing problems in the field have been fixed.

All boards manufactured since May 1989 should have the correct
crystals, including all version 3 MCIs.

Boards with the wrong crystals still interoperate with most other
equipment.

You can identify suspect boards by inspecting the ethernet encoder
crystals, which are near the ethernet connectors on the board.  The
out-of-spec crystals are tiny little things (.2 x .2 x .5 inches or so)
labeled "fs200".  Anything else is correct.

William  Westfield
cisco Engineering.
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