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Date:      Wed, 24 Apr 1996 17:21:22 +0300 (EET DST)
From:      Narvi <narvi@haldjas.folklore.ee>
To:        "Rodney W. Grimes" <rgrimes@GndRsh.aac.dev.com>
Cc:        davidg@Root.COM, hasty@rah.star-gate.com, scrappy@ki.net, current@FreeBSD.org, hackers@FreeBSD.org
Subject:   Re: Intelligent Debugging Tools...
Message-ID:  <Pine.BSF.3.91.960424171951.19893A-100000@haldjas.folklore.ee>
In-Reply-To: <199604240832.BAA04088@GndRsh.aac.dev.com>

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On Wed, 24 Apr 1996, Rodney W. Grimes wrote:

> > >5. make sure that one of the drives is sending the termination power
> > 
> >    For external termination, this is normally done by the controller, not any
> > of the drives.
> 
> True.
> 
> > Most people terminate the last drive with the drive's termination
> 
> I would disagree with that, most people use an external terminator on
> an external chain.  Turning terminators on inside of external scsi
> enclosures is a no no in my book, it often leads to multiple termination
> when someone not so informed adds something to a chain.  Or middle
> termination with a floating end when a chain gets swapped around.
> 
> > and configure that drive to supply it's on termination power
>                                           ^^ own
> For external scsi chains of any length > 3 feet I would _strongly_ encourage
> the use of drive supplied termination power (preferably from the last
> drive on the chain) to the scsi bus.  
> 
> > (which is usually the factory default).
> 
> With the advent of the SCSI PnP spec this and other defaults are rapidly
> changing, the SCSI PnP spec requires that drives ship with no termination
> enabled, the use of on drive termination is verboten, you are suppose to
> use cable end terminators both internally and externally.  I don't seem
> to recally anything about term power though :-(.

There happen to be devices (at least my HP DAT is of that kind) which 
always supply termination power - you even can'tr turn it off.

> 
> -- 
> Rod Grimes                                      rgrimes@gndrsh.aac.dev.com
> Accurate Automation Company                 Reliable computers for FreeBSD
> 

	Sander

Eat good food, preserve nature, be nice to all nice people :)



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