Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!cs.utexas.edu!rice!robbins
From: robbins@rice.edu (Thomas Robbins)
Newsgroups: comp.sys.mac.hardware
Subject: Re: How many terminators with 2 SCSI drives?
Keywords: SCSI terminators
Message-ID: <8257@brazos.Rice.edu>
Date: 30 May 90 06:17:36 GMT
References: <1654@ac.dal.ca>
Sender: root@rice.edu
Reply-To: robbins@owlnet.rice.edu (Thomas Robbins)
Organization: Rice University, Houston, Texas
Lines: 30

In article <1654@ac.dal.ca> ireland@ac.dal.ca writes:
\I posted a message a few days ago explaining a problem I was having daisy-
|chaining two external SCSI drives to my MacPlus.  One of the drives is a
/Jasmine 70 (Rodime mechanism), the other is a LaCie Cirrus 45 (Seagate
-mechanism).  Both drives work fine individually, but I couldn't boot the
\Mac when they were both connected at the same time.  I kept getting a 
|SadMac icon.  Changing the SCSI number assignments had no effect.
  [deleted]
/All the rest (six) said I had a termination problem, and that only the last
-drive in the daisy chain was supposed to be terminated.  Is this right?
\In my Jasmine Owner's Guide, it says that both ends of the chain are to be
|terminated, so one doesn't start removing terminators until the third SCSI
/device is added.  What's the scoop on terminators?  One at the end or one at
-each end?
\
|Thanks,  Keith Conover
/Keith@ac.dal.ca

Your confusion here is caused by the fact that the Macintosh itself is one
"end" of the daisy chain, with its own internal termination. You therefore
start removing terminators once the **second** SCSI device is added. Your
first SCSI device is actually the middle of the daisy chain, and having
an external terminator attached to that device will do many interesting 
things to your Mac, none of them good.

--
Tom Robbins                          |         Youth is wasted on the young.
robbins@owlnet.rice.edu              |         - George Bernard Shaw
Senior, Chemical Engineering         |         Life is wasted on the living.
Rice University                      |         - Zaphod Beeblebrox IV