Fixed sense data valid bit and MMC-5

Douglas Gilbert dougg at
Sun Feb 20 00:16:20 PST 2005

* From the T10 Reflector (t10 at, posted by:
* Douglas Gilbert <dougg at>
SPC-3 rev 21d states in section 4.5.3 on fixed format sense
data: "A VALID bit set to zero indicates that the INFORMATION
field is not defined in this standard or any other command
standard (see 3.1.18). A VALID bit set to one indicates the
INFORMATION field contains valid information as defined in
this standard or a command standard."

SBC-2 complies with this and disks that I test do indeed
set the VALID bit when they report a MEDIUM ERROR. However
I am seeing a CD/DVD combo drive report a MEDIUM ERROR
with an INFORMATION field set to a very likely lba but
the VALID bit is clear. Further, when I look at MMC-5 it
discusses reporting MEDIUM ERRORs and setting the INFORMATION
field but no mention of the VALID bit.

If the CD/DVD drive I am testing reflects common practice
(i.e. following MMC) then perhaps the statement in SPC-3
needs to be weakened or a note added. Perhaps MMC-5 could
make a statement about the VALID bit as well.

Doug Gilbert

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