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Date:      Mon, 20 Apr 1998 00:17:02 -0700 (PDT)
From:      dan@math.berkeley.edu (Dan Strick)
To:        dkelly@hiwaay.net, shocking@prth.pgs.com
Cc:        dan@math.berkeley.edu, hardware@FreeBSD.ORG
Subject:   Re: Narrow SCSI controllers, and using WIDE drives with them
Message-ID:  <199804200717.AAA02451@math.berkeley.edu>

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> > Is it possible, and if you have one of those 50 pin flat ribbon cables,
> > is it possible to buy adaptors for those D-plug style connectors?
> 
> Yes, it is possible to buy adapters. No, it won't work. As a general 
> rule wide HD's will not fall back to a narrow connection. Wide 
> controllers are forced to fall back and handle narrow devices as a 
> special case.

I think the intent of the SCSI-2 standard is that wide transfers be
attempted only if both SCSI bus nodes and the cable between them are
wide and that the required tansfer parameter negotiation should
somehow fail otherwise.  I don't recall the details.

I concede that the SCSI bus manufacturers have in the past demonstrated
an unexpected ability for evading obviously desirable features of the
SCSI standards when concentrating exclusively on immediate marketing
concerns.

It ought to work by default.  If not, you may be able to tell the
host adapter via its BIOS interface to only do narrow transfers
with specific SCSI devices.

Dan Strick
dan@math.berkeley.edu

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