4D20, 25, 70, 80 and 85s and most Power Series machines can boot only
  from SGI CD-ROMs or later Toshiba 3401s which have SGI firmware
  activated by the modification described below. (Newer Toshiba models
  don't have that firmware and won't work.) Older SGIs can boot only
  from a local tape drive or over the network. Newer machines (4D30 and
  35s, Indigos, Challenges, Onyxes, Indys, Indigo^2 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.

  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] CD-ROM 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

  Darrell A. Gentry <dar@dar.net> points out that if '0' is on the right
  and '1' on the left, you should believe the numbers, not the
  locations, and that although 3401s can no longer be bought new, they 
  can be bought cheaply on misc.forsale.computers.storage for about $30.

  Ramani Pichumani <ramani@stanford.edu> says that Toshiba's XM3701B
  6.7X CD-ROMs with recent ROMs (look for "Version No. 005, ROM Version
  NA60123" on the bottom) work well on Indigos for both data and audio.
  Tobias Kunze <t@kunze.stanford.edu> confirms that they can be booted
  from. You may be able to get a ROM upgrade from Toshiba, but be sure
  not to mention that you want to use the drive on an SGI.

  Robb Masters <rsm@cybermagic.net> summarized information on many
  third-party drives; see
  ftp://viz.tamu.edu/pub/sgi/hardware/cdrom/3rd-party.  Jerry Fountain
  <gof@chem-eng.nwu.edu> provided info and software for an NEC-3Xe; see
  ftp://viz.tamu.edu/pub/sgi/hardware/cdrom/NEC-3Xe/.  Carsten Koch's
  writeup on CD-ROM writers (see below) also has some useful comments on
  CD-ROM usage under IRIX in general.