Comments on 05-177r0 "write same"

Curtis Stevens curtis.stevens at
Wed May 4 12:54:54 PDT 2005

* From the T10 Reflector (t10 at, posted by:
* "Curtis Stevens" <curtis.stevens at>

	I am confused by your issue.  This only thing you need to check is
word 206 bit 2.  If it is 0, you can't use LBA Segment Access.  If it is 1,
you can.  The method of detection is contained in the technical report.

Curtis E. Stevens
20511 Lake Forest Drive #C-214D
Lake Forest, California 92630
Phone: 949-672-7933
Cell: 949-307-5050
E-Mail: Curtis.Stevens at
Ambition is a poor excuse for not having enough sense to be lazy.

-----Original Message-----
From: James.C.Hatfield at [mailto:James.C.Hatfield at] 
Sent: Wednesday, May 04, 2005 12:47 PM
To: Curtis Stevens
Cc: t10 at
Subject: RE: Comments on 05-177r0 "write same"

You are correct in stating that there is no documented standard
way to 'enable or disable' SCT LBA Segment Access, but there <is> a
documented way for the device to separately report that
     a) it supports (or not) SCT (in general)     <and>
     b) is supports (or not) SCT LBA Segment Access

It is vendor unique whether or not there is a way to change the settings
of these bits.

Please refer to the SCT Technical report (1701DT rev 5, page 5)
      IDENTIFY DEVICE, word 206
      bit 0 = SCT Feature set supported (includes SCT status)
      bit 2 = LBA Segment Access (AC2) supported

I request that the SAT document needs to address what to do if bit 0 is set
to one
and bit 2 is cleared to zero.

Thank You !!!
Jim Hatfield
Seagate Technology LLC
   e-mail:  James.C.Hatfield at
   s-mail:  389 Disc Drive;  Longmont, CO 80503 USA
   voice:  720-684-2120
   fax....:  720-684-2711

(from Curtis Stevens' notes of the discussion at the SAT meeting May 3

1. OPCODE - Is there a preferred hierarchy of choices for implementation?
      If a device does not support SCT, is there a preference for the other

      Committee Respose:
      a. Wording was changed to reference SCT LBA Segment Access.
      There is no enable or disable for this capability.

3. Please clarify the meaning of "device implements SCT".  See 1a above.

4. What if the ATA device (target) 'supports' SCT, but does not have it (or
the LBA Segment Access subcommand) enabled?

Committee Response:
      There is enable/disable for SMART, but there is no enable or disable
for SCT.

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