Discussion about 11-376 -- add extension for defect descriptors

Gerry Houlder gerry.houlder at seagate.com
Tue Sep 20 14:40:55 PDT 2011

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Hi everyone,
During discussion of 11-376r0 at the September CAP meeting, I was given
direction to use two new address descriptor values for the new Bytes From
Index and Cylinder Head Physical Block formats. If I do this, this will
consume two of the three reserved codes.
Before I do this, I'd like to point out that the currently defined address
formats are not very applicable to Solid State Drives. I suspect these
drives use the vendor specific option today, if they support any of the
options at all. Is there any thought that there needs to be standard defect
descriptor formats that are designed for SSD use? If so, then it might
*not*be a good idea to consume two of the three remaining defect list
formats for
HDD use.
This direction was instigated by the head field not being able to give up
one of its bits for the MADS function. If the bit was carved from the most
significant bit of the four byte BYTES FROM INDEX or SECTOR NUMBER fields,
would this make it more acceptable to extend the current address descriptor
formats instead of creating new ones?
I'd like to see more discussion on whether new address formats are needed
for SSD or other new technology products before committing to using up two
more address descriptor formats. Note that we are constrained by the 3 bit
field in the FORMAT command to a maximum of 8 address formats. However, I
suppose this could be expanded if SBC-3 reclaimed the two obsolete bytes in
the FORMAT CDB, the 111b code could be a trigger to get the actual address
descriptor format from of of these bytes ...

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