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From: olson@anchor.esd.sgi.com (Dave Olson)
Newsgroups: comp.periphs.scsi,comp.sys.ibm.pc.hardware
Subject: Re: How much should I pay for a SCSI cable (with 3 or 4 connectors)?
Message-ID: <hd11610@zola.esd.sgi.com>
Date: 20 Apr 93 00:55:51 GMT
References: <1993Apr13.071353.852@ica.philips.nl> <T83y2B1w164w@hub.parallan.com>
Sender: news@zola.esd.sgi.com (Net News)
Organization: Silicon Graphics, Inc.  Mountain View, CA
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In <T83y2B1w164w@hub.parallan.com> danj@hub.parallan.com (Dan Jones) writes:
| > >Also, I seem to remember a posting saying that the SCSI spec calls for
| > >1 foot between devices on the cable, but most cables you get (internal)
| > >don't meet the spec.
| 
| SCSI II Draft Proposal, Rev. 10h, Section 4.2.1: Single-Ended 
| cable, which is in the Cable Requirements Section, has an 
| implementor's note: " Stub clustering should be avoided. Stubs 
| should be spaced at least 0.3 meters apart."
| 
| For the non-technical, stubs are SCSI devices. :-)

However, also be aware that Implementor's notes are basicly
recommendations, they are *NOT* part of the spec.  As others have
noted, many vendors (including SGI) violate this.  Indeed, the main
point is to reduce impedance changes, and therefore reflections, and
therefore 'noise' on the bus.
--
Let no one tell me that silence gives consent,  |   Dave Olson
because whoever is silent dissents.             |   Silicon Graphics, Inc.
    Maria Isabel Barreno                        |   olson@sgi.com
