[t13] SCSI ATA f/w revision bytes how many

Pat LaVarre p.lavarre at IEEE.org
Tue May 25 17:34:10 PDT 2004

* From the T10 Reflector (t10 at t10.org), posted by:
* Pat LaVarre <p.lavarre at ieee.org>
> "CDBs of arbitrary sizes up to a generous limit".

Yes.  The FireWire CDB length limit of x3E8 = 1000 is the largest I've 
seen anywhere in SCSI pass thru, almost 4X the common limit of xFF = 

> the ORB_size field in the Unit_Characteristics entry
> in configuration ROM specifies a target's ORB size
> as a multiple of quadlets. Since it's an 8-bit field,
> ORBs are constrained to be less than
> or equal to 1020 bytes in length.

Ah, that fits.

x3FC = xFF * 4 = 1020 = 255 * 4 bytes.  That leaves 1000 max for the 
CDB once we lose the x14 = 20 = 5 * 4 bytes to the rest of the ORB that 
is the wrapper around the CDB.  We end with 1000 = x3E8 that looks like 
a decimal limit, but is actually a hex limit i.e. x400 - x18.

Pat LaVarre

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