Obsoleting non-standard Disk use of mode page code 0Dh

Ralph Weber ralphoweber at CompuServe.COM
Fri Sep 15 04:12:13 PDT 2000

* From the T10 Reflector (t10 at t10.org), posted by:
* Ralph Weber <ralphoweber at compuserve.com>
An SPC-2 Letter Ballot comment, from me, requests that
the Disk usage of mode page code 0Dh be made obsolete.
I intend to accept that comment unless a really good
counter argument is presented soon.  The history of
the Disk usage of mode page code 0Dh and why it should
be made obsolete are as follows.

Way back in 1991 or 1992, X3T9.2 approved the use of mode
page code 0Dh by Disks as the Power Condition mode page
(see document X3T9.2/91-014r6, if you can find it).  Later,
it was agreed to change the mode page code for the Power
Condition mode page from 0Dh to 1Ah so that all device
types could have a Power Condition mode page.  Mode page
code 0Dh cannot be used in this way because CD-ROM
devices use it for the CD device parameters mode page.

To give disks some leeway for converting from 0Dh to
1Ah, the Power Condition usage of 0Dh was documented
in SPC Annex B in the numeric list of mode page codes
and uses.  A note was provided mentioning the
X3T9.2/91-014r6 document and stating that mode page
code 1Ah should be used wherever possible.

The SPC editor caught some serious flack from X3 (now
NCITS) and ANSI over have a reference to a committee
document in SPC, but we prevailed and SPC was published
with the reference to X3T9.2/91-014r6, although the
words around the reference had to be modified.  The
SPC-2 editor is not inclined to fight with NCITS and
ANSI over a document from a committee that has not
existed for nearly seven years now.

Therefore, the Disk usage of mode page code 0Dh
needs to be made obsolete.

As one final note, I'll add that this is a non-
substantive change because the annex in question
is informational.



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