IGNORE WIDE RESIDUE Message

Brian A. Berg bberg at bswd.com
Fri Nov 27 07:16:35 PST 1998


* From the T10 (formerly SCSI) Reflector (t10 at symbios.com), posted by:
* bberg at bswd.com (Brian A. Berg)
*
Norbert:

Since it is not possible to know the number of bytes that will ACTUALLY
get transferred by a SCSI command, this message is indeed necessary.
In other words, the transfer count is what is requested, but not
necessarily what is experienced.  I have found this message to be
particularly important with tape drives.
___________________________________________________________________
 Brian A. Berg            bberg at bswd.com        Voice: 408.741.5010
 Berg Software Design                             FAX: 408.741.5234
 P.O. Box 3488         http://www.bswd.com/
 14363 Saratoga Ave., Suite 200      Consulting: SCSI, storage, I/O
 Saratoga, CA 95070 USA

> * From the T10 (formerly SCSI) Reflector (t10 at symbios.com), posted by:
> * "Norbert Lewalski" <norbert_lewalski at vortex.de>
> *
> IGNORE WIDE RESIDUE message has been defined in the SCSI-2 
> specification and is also part of the SCSI-3 specification. As we 
> have never seen such a message being sent by a target we wonder if 
> anyone has ever made use of this message or will do so in the future. 
> 
> If wide transfer has been negotiated between initiator and target and 
> transfer count is an odd number of bytes, then the message is not 
> required as both sides know that the high byte of the last word 
> transfered must be ingnored.
> 
> If wide transfer has been negotiated and transfer count is an even 
> number of bytes, then why should the target disrupt the transfer at 
> an odd number of bytes?
> 
> Regards,
> Norbert Lewalski
> 
> 
> 
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