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From: marks@pro-shop.cts.com (System Administrator)
Newsgroups: comp.sys.apple2
Subject: Re: Re- Much about Quantums and
Message-ID: <8067@crash.cts.com>
Date: 18 Mar 91 00:36:14 GMT
Sender: root@crash.cts.com
Lines: 45

In-Reply-To: message from toddpw@nntp-server.caltech.edu

>>SCSI drives are supposed to		Not like
>>look like
>>
>>	[]--|	  |--[]				[]-----[]
>>	    |	  |					|
>>	    |	  |					|
>>	    |_____|					|
>>	       |					|
>>	       =					=
>
>Aw shucks. My HDI PowerDrive (quantum 105s mech.) does it the 'bad' way.
>
>I understand why there's more noise in the second configuration, though.
>Electrically, you're splitting the signal as it passes through the drive,
>and there will be reflections and other wave effects at high transmission
>rates, which manifest themselves in the form of noise.
>
>Todd Whitesel
>toddpw @ tybalt.caltech.edu

Todd,
  It is most probable that the signal doesn't pass through your drive, but
loops out to the other drive before it gets to the first. There shouldn't be
any noise from this setup.

   []==|___|======[]
       |     
       |
       |
       =
 
More like this if you can see what I mean. If you open up your drive case you
will see that the two plugs are directly connected, and only one lead runs to
the drive. While you've got the drive case open look at the bottom of the
drive itself and you will see the terminating resistors. They are right above
the molex plug, unless your drive is not a self terminator.(Most Seagates,
and Conner are. I'm not sure about Quantums) That might be a source of line
noise, as feedback due to a bad resistor or not enough resistance inline.

-- Mark
----
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