Format Unit SI bit

Mark Evans Mark.Evans at
Fri Jun 3 08:56:05 PDT 2011

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Hi Truong,
The SI bit was added into the INITIALIZATION PATTERN DESCRIPTOR for the
FORMAT UNIT command in SBCr-05 based on proposal 96-186R1.  As you wrote the
definition of the bit was modified slightly in SBC-r06 as the result of
discussion at the SCSI working group meetings in October of 1996.  The
definition of the SI bit has not been changed since that time.
What I think we really intended the new wording to mean is, "If the SI bit
its set to one, then the device server shall ignore:
a)	 the FMTPINFO field;
b)	the FMTDATA bit;
c)	 the CMPLST bit;
d)	the DEFECT LIST FORMAT field;
e)	 all of the bits and fields in the parameter list header, except the
IMMED bit; and
f)	  any defect list data.
Others may correct me if I'm wrong.  You know who you are, and I'm sure you
will - ha!
Please feel free to call or send an email to me with any comments or
questions that you have about this stuff. 
Mark Evans
Western Digital Corporation
5863 Rue Ferrari
San Jose, CA 95138
Email: mark.evans at
From: owner-t10 at [mailto:owner-t10 at] On Behalf Of Truong
Nguyen - SISA
Sent: Thursday, June 02, 2011 5:54 PM
To: t10 at
Subject: Format Unit SI bit
In SBC3r27, in the Format Unit initialization pattern descriptor subclause, there is a statement regarding the SI bit precedence:
"An SI bit set to one shall take precedence over any other FORMAT UNIT CDB
What is this statement supposed to mean specifically?
It seems as though the statement was added some time ago in SBCr6:
"Clarified SI by adding the statement An SI bit set to one shall take
precedence over any other FORMAT UNIT field."
I could not find any proposals associated with the modification.
Truong Nguyen
Samsung Information Systems America

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