----- Original Message -----
From: <trag at io.com>
To: <undisclosed-recipients:>
Sent: Thursday, July 09, 2009 4:05 PM
Subject: Re: Classic mac fun (and some questions)
(continued...again...)
From: "Jeff Walther" <trag at
io.com
To: cctech at
classiccmp.org
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> Date: Thu, 9 Jul 2009 12:00:48 -0400
> From: Ethan Dicks <ethan.dicks at
gmail.com
I tried to look that up and found it easy to see
that the IIfx needed
something odd (I couldn't find specifics), so well done there. It
would be interesting to get the details to see where Apple went off
the rails from the SCSI spec.
IIRC, it's a matter of adding a capacitor and maybe a resistor to a
regular terminator. There's an Apple Technical Note or similar available
somewhere. I probably have a copy squirreled away on my hard drive at
home. And I think I remember that they use a somewhat higher value
capacitor (so add a smaller one in parallel on an existing terminator) and
a lower resistance (so again, add a resistor in parallel). But I could
be misremembering.
Again, IIRC, the IIfx's SCSI was too noise sensitive. But I've also
heard/read that that was only true for the early production run and that
the later built machines did not need the funny terminator.
Neither of my IIfx systems need that terminator to work.