Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uunet!mcsun!ukc!icdoc!qmw-cs!liam
From: liam@cs.qmw.ac.uk (William Roberts)
Newsgroups: comp.protocols.appletalk
Subject: Re: Connecting to Ethernet
Summary: Comments on Apple card and Kinetics EtherPort II
Message-ID: <1733@sequent.cs.qmw.ac.uk>
Date: 2 Mar 90 11:23:25 GMT
References: <Added.QZvKztG00Ui38=OU8w@andrew.cmu.edu>
Reply-To: liam@cs.qmc.ac.uk (William Roberts)
Organization: Computer Science Dept, Queen Mary and Westfield College, U of London, UK.
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We've had no troubles with our mixture of Apple EtherTalk cards
and Kinetics EtherPort II cards (both NuBus ones) except under
automatic reconfiguration of A/UX. The problem is subtle but
devastating, though it does not affect normal use of a
configured machine.

The snag is that Apple's guidelines don't say anything about
when NuBus interrupts from the card should be enabled (on the
card). Kinetics enable the card to generate interrupts as part
of the initialisation firmware executed by the Mac II from the
card ROMs. The Mac design doesn't allow for disabling of
individual card interrupts, and to clear an interrupt you must
understand the particular type of card and know what to do to
clear it.

Normally this is OK; the Slot Manager will have opened the
driver anyway. However, under A/UX, when doing the
autoconfiguration the kernel used is a bare minimum and has no
such drivers. If the card is still connected and the Ethernet
is active, then the Kinetics card will generate an interrupt
and Bingo, your machine is locked up. The Apple card naturally
doesn't do this, but Apple should have stated explicitly in
their design guidelines that you must only enable the card
interrupts from the initialisation routine in the Operating
System driver.

Don't know about co-processor cards, but it should be possible
to do good things with them.
-- 

William Roberts                 ARPA: liam@cs.qmw.ac.uk
Queen Mary & Westfield College  UUCP: liam@qmw-cs.UUCP
Mile End Road                   AppleLink: UK0087
LONDON, E1 4NS, UK              Tel:  01-975 5250 (Fax: 01-980 6533)