SBC-2 mandatory vs optional commands

Pat LaVarre p.lavarre at
Tue Jul 20 13:34:17 PDT 2004

* From the T10 Reflector (t10 at, posted by:
* Pat LaVarre <p.lavarre at>
> Leave the 32 byte commands as strictly optional.  32 byte CDB support 
> is
> still very rare, as is support for XOR commands.

Yes please.

An SPC that requires more than 12 bytes per CDB is an SPC that won't 
fit into PATAPI/ SATAPI today.

is my guess, because I've never seen an actual PATAPI allow more than 
12 bytes per CDB, even though since about the beginning the option for 
as many as 16 was published.  And to allow more than 16, someone will 
have to revise the PATAPI/ SATAPI texts.  Of course, we can always 
exacerbate the degree to which MMC consciously overrides SPC, and there 
say that so-called requirement of SPC becomes optional for MMC.  Then 
the PATAPI/ SATAPI CDB length limits only force us to mischaracterise 
RMB devices that are not MMC devices.

Pat LaVarre

[P.S. Thank you to the person who brought me to this thread offline.]

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