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Help with Amiga SCSI interface?

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The Question is:

 
I have a 4mm DAT drive, known working and recently removed from an OpenVMS
system.  I have it connected to (don't laugh) an old Amiga 2000.  Writing my
own software I am able to issue SCSI packets to the tape drive, but can't
seem to get a particular beha
vior I enjoyed under VMS, using $QIOW with the "Read Virtual Block"
function.  Namely, I could read blocks off the tape without knowing their
sizes in advance, by requesting the LARGEST POSSIBLE blocksize -- 65536
bytes -- and picking up the "actual size"
 out of the IOSB after the read completed.  Issuing simplistic SCSI "READ"
commands to the tape drive nowadays, I seem to have to specify the correct
block size "up front" in order for the read to succeed.  I'm thinking that
the VMS tape-driver programmer
s knew more about SCSI than I do, and that they knew a SCSI-command sequence
that I don't, to get the drive to behave "the VMS way" I've described above.
So... can you tell me the specific sequence of SCSI commands issued to a 4mm
DAT drive in order to p
erform the following VMS DCL commands --
 
   INITIALIZE/OVERRIDE=(OWNER,ACCESS,IDENT) devicename:
 
   MOUNT/FOREIGN devicename:
 
   MOUNT devicename: label
 
-- and for a QIO[W] IO$_READVBLK specifying a record (block, buffer) size of
65536 bytes?  I'd really appreciate knowing the magic sequence(s).  Thanks
in advance.
 


The Answer is :

 
  Please contact the Amiga Wizard for assistance with this question.
 
  The OpenVMS Wizard is not in a position to provide SCSI programming
  tips for the Amiga operating system, and is entirely unfamiliar with
  the Amiga system and its SCSI interface(s).
 
  The particular series of SCSI commands generated by OpenVMS can vary
  over OpenVMS releases, and is considered undocumented.  (The lowest
  level of the SCSI interface that is documented is in the area of the
  GKDRIVER, see the I/O User's Reference Manual for details.)
 
  Available tools include SYS$ETC:SCSI_INFO, available in V6.2 and
  later OpenVMS releases.
 
  Please start with the SCSI specifications for the particular version
  of SCSI in use on the Amiga, and (if you have access to these) the
  OpenVMS Source Listings CD-ROM set and a SCSI bus analyzer.
 

answer written or last revised on ( 1-MAR-1999 )

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