Queue tag size in Packetized SCSI?

Gerry_Houlder at notes.seagate.com Gerry_Houlder at notes.seagate.com
Tue Mar 7 20:59:15 PST 2000


* From the T10 Reflector (t10 at t10.org), posted by:
* Gerry_Houlder at notes.seagate.com
*
Parallel SCSI historically has an 8 bit tag value. however the packetized
structure allows space for a two byte tag value. Most FC implementations
typically use a two byte value for the equivalent of the tag value.

An implementation today is restricted to 8 bit tag value for compatibility with
non-packetized parallel SCSI. There is room for a future enhancement that dumps
compatibility with non-packetized SCSI and allows two byte tag value, however.





"Kendall, Guy" <Guy.Kendall at lsil.com> on 03/07/2000 02:59:16 PM

To:   t10 at t10.org
cc:    (bcc: Gerry Houlder)

Subject:  Queue tag size in Packetized SCSI?



* From the T10 Reflector (t10 at t10.org), posted by:
* "Kendall, Guy" <Guy.Kendall at lsil.com>
*
In SPI-3, revision 13.a in section 14.3.2, the TAG field is shown at 16 bits
in the SPI L_Q. The text describing this field says "The tag is an 16 bit
unsigned integer..." Then it refers you to section 16.4.1 for more details
on tags. In section 16.4.1, it says "The TAG field is an 8-bit unsigned
integer..." and goes on to say "For each logical unit on each target, each
application client has up to 256 tags to assign to tasks".

So are tags 8 or 16-bit for packetized SCSI (Information Units enabled) ?

Thanks,
Guy
*


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