[gmcenroe]

OK going to hit the high points quickly:

If you are referring to this drive:
https://hifiduino.files.wordpress.com/20...c_rev1.pdf

I am using a similar CDROM XM-6201B drive made in 1998. There are no manuals online for this unit.

You will never be able to boot Irix media, nor read Irix-only application CDs.  This drive does not have support 512 Byte block mode (no rear jumper for it).  It will work with Audio CDs and normal ISO9660 stuff using normal 1024 byte block mode. But it will never install Irix using it nor read Irix-only media.  It's not able to support reading CDs like a hard drive (common trick for SUN and SGI stations).

The drive does not even recognize audio CDs, If I try to play them, the Indigo 2 reports No CD loaded, so there must be another problem with the drive, Also according to an old report from an SGI employee Dave Olsen he reported the following: 
 
 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.

So unless The 6201B cannot transmit at this lower byte rate when instructed by software I am not sure if this applies.


 You may also need to set the jumpers to enable parity to be in full compliance (HDDs too)  The front bays are SCSI ID 1,2,3 from lower right, moving up. Technically you can use ID 6 if you want (no harm).  But must Irix instructions for typing in commands assume ID is 3 for Indigo2. Just saying. 

I think SGI hardware manager says any SCSI ID 0-7 is fine as long as they are not duplicated. When I set the jumper to enable parity on bootup the Drive does not show up or get reported on hinv so this must be set to off.

I may try older CDROM drives such as the xm3501b, or xm5301b which are reported to work on Indigo2 again no manuals for these online. Since I recall that I used my old XM6201B drive to install IRIX 6.5 even though that was 15 years ago I don't see why I am having problems with this drive unless the unit I bought on ebay is defective. I have no other hardware to test it on.
 
 

Good luck.