From: paws@spam.cray.com (Daniel Baehr)
Subject: Re: LUN 1 SCSI device
Organization: Cray Research, Inc.
Date: 12 Aug 92 09:27:22 CDT


In article <1992Aug11.203905.11589@ninja.zso.dec.com>, Hans Ridder <ridder@zso.dec.com> writes:
> In article <1992Aug11.072220.18797@walter.cray.com> paws@spam.cray.com (Daniel Baehr) writes:
> >
> >In article <10AUG199216433778@vx9000.weber.edu>, alewis@vx9000.weber.edu (ALEWIS) writes:

> >  In the world of SCSI there is no such thing as a LUN of ANYTHING other
> > than 0.  The SCSI ID, on the other hand, can be from 0-7.  There are
> > ways of putting more than 8 devices on a SCSI chain but that isn't 
> > supported on the Amiga.  Grab yourself an ANSI SCSI spec and read all
> > about it.
> 
> I suggest you grab an ANSI SCSI spec. and read all about it.  What would
> be the point of having LUN's if they always have to be 0?  Please check
> your facts before posting such nonsense.

   In the most receint copy of the spec that I have they call the LUN 
 what we call the SCSI ID and the SCSI ID is the address present on the 
 databus when a device needs attending to.  I thought the definition of 
 LUN we were using was more inline with the way I*M uses it?

> 
> Also, to clarify, there are *only* 8 SCSI ID's which means that there
> can be *only* 8 SCSI devices connected to one bus.  Except for semantic
> arguments over whether a LUN is device, there is no way to get more than
> 8, as you claim.  The system's Host Adapter (commonly incorrectly
> referred to as a "controller") counts as one device, so that limits
> number of additional SCSI devices to 7.

   Correct.  I should not have said there WAS a way to put more SCSI 
 devices on a chain.  Stupid of me.  It was something that I read that I 
 didn't understand correctly when I read it the first time.

> 
    [ stuff deleted ]
 
> That's silly.  Where in the world does it say "the controller should
> allways [sic] be ID 0?"  Go see what the SCSI spec. calls a controller.

   That point I took from a setup manual for one of my controllers.  It "suggested" that you not use one of the SCSI IDs because
 the controller used it, as you pointed out above.  I should not have 
 said "proper".

> 
> >| Daniel Baehr Work: paws@spam.cray.com  Home: daniel_baehr@bearsden.UUCP|
> 
> As to the original poster's question, I believe the A2091 has a jumper
> to enable LUN support.  I have no idea if it really works.  I seem to
> remember the A3000 has a bit in the "battmem" which is supposed to do a
> similar thing.  Since at least one of the SCSI related items in the
> battmem is ignored, who knows if the LUN bit (if it exists) is checked
> by the driver software.

    As was pointed out to me in e-mail some older SCSI drives used the I*M
 style of LUN addressing.  I called IVS and I was told they support it.
 I not sure which definition of LUN he was using.

> 
> -hans
> -- 
>   Hans-Gabriel Ridder				Digital DECwest Engineering
>   ridder@rust.zso.dec.com			Bellevue, Washington, USA
>   {pacbell,pyramid,uunet}!rust.zso.dec.com!ridder


     Daniel Baehr
--
+------------------------------------------------------------------------+
| Daniel Baehr Work: paws@spam.cray.com  Home: daniel_baehr@bearsden.UUCP|
| These OPINIONS are mine and mine alone.                                |
+------------------------------------------------------------------------+