Subject: ! -40- Can I use a non-SGI CD-ROM on my SGI?
Date: 08 Dec 1995 00:00:01 EST

  4D20, 25, 70, 80 and 85s and most Power Series machines can boot only
  from SGI CD-ROMs. Older machines can boot only from a local tape
  drive or over the network. Newer machines (4D30 and 35s, Indigos,
  Challenges, Onyxes, Indys, etc.) have smarter PROMs and can boot from
  at least some third-party CD-ROMs, for example the Sony and Toshiba
  drives intended for Suns. The rest of this entry discusses what
  qualifies a drive for 4D30s and later.

  Dave Olson <olson@sgi.com> of SGI says, The basic requirement for
  Indigos is that the drive be set to use a 512 byte block size.  Since
  Indigos don't reset the SCSI bus on reboot or halt, you *might* be
  able to boot your machine in some other way, set the CD-ROM's
  blocksize with a devscsi program while the system is up and then
  install from it, but I won't swear to it. Late R4K Indigos, Indys,
  Indigo2s, and Onyx/Challenges all know how to set the block size if
  the drive identifies itself as a CD-ROM, reports the block size as
  something other than 512 bytes in the block descriptor and accepts
  the new block size in the block descriptor.

  Rob Silvers <rsilvers@nynexst.com> reports that he has been
  sucessfully using a third-party dealer's Toshiba TXM3401E1 on an
  Indigo. It cost about $760. It is physically larger than an external
  Apple or Next drive. It is double speed and handles multi-session
  photo-CDs.  'cdromd', 'inst' and 'cdman' work, but he has not tried
  to boot from it as of 12 June 93.

  Bart Richards of Thunderstone Software <bart@thunderstone.com>
  writes, The following minor surgery makes a run of the mill Toshiba
  3401[B|E] CDROM drive SGI [Indigo] or Sun-compatible. I got it
  straight from an anonymous Toshiba Tech. guy, and it worked for me.

  There are two solder pads located on the circuit board at the back
  right corner of the drive's aluminum housing when viewed from the top
  with the SCSI connector facing away from you. These may or may not be
  labeled as '0' & '1', but '0' is on the left and '1' is on the right
  (or closest to the edge of the circuit board).  The normal state for
  these solder pads from the factory is for both of them to be closed.

  With an Exacto Knife or soldering iron (whichever is appropriate for
  the desired configuration), cut or solder these pads to match the
  entries in the following table:

                                                  +++___++++++++__
                                                 |power   SCSI    |
  '0'   '1'  O=CUT/OPEN S=SHORTED/SOLDERED       |              01|
  ----------                                     |----------------|
   S     S   Toshiba Default (2048 byte block)   |                |
   S     O   512 byte blocks                     |     TOP        |
   O     S   SGI ( Bootable )                    |     OF         |
   O     O   Sun / Integraph                     |     DRIVE      |
                                                 |                |
                                                 |                |
                                                 |                |
                                                 |________________|
                                                        DOOR

+ Jerry Fountain <gof@chem-eng.nwu.edu> provided info and software for
+ an NEC-3Xe; it's in ftp://viz.tamu.edu/pub/sgi/hardware/cdom/NEC-3Xe/.