Re: SCSI termination...

[derek@slab.slip.uiuc.edu (Derek Taubert)]

In article <k171551@pro-newton.cts.com> danb@pro-newton.cts.com (Dan Brown)  
writes:
> In <1993Nov1.144533.5156@seq.uncwil.edu>
> caroon@seq.uncwil.edu (Craig N. Caroon) writes:
> 
> >Question:  Should only the last device on a scsi chain be terminated, or
> >		   should both the first and last be terminated?
> 
>         Both ends of the chain should be terminated.

Don't get the wrong idea about this, thou...  Both ends need to be electrically
terminated, but this doesn't necessarily mean that you have to place a
"terminator device" at both ends (better know as an external terminator).  Most
SCSI host interfaces (with the particular exception of one of the MAC models,
I forget which) have the terminating resistors for that end built into the
card (better known as an internal terminator).  Quite a few SCSI drive
mechanisms have the terminator for the other end built in as well (look for 2
resistor networks near the 50 pin connector).  In these situations, all you
need is a cable.

If you're talking about having multiple drives connected to one SCSI card, the
card needs to be terminated, and the last drive on the cable needs to be
terminated (* = internal or external terminator, NOT BOTH!).  This also
requires removing any internal terminating resistor networks from the middle
drives.

 *=========+=========+=========*
Host    Drive 1    Drive 2   Drive 3

Hope this answers your question...

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Derek Taubert                   |  Ask me about TCP/IP for the Apple IIgs!
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