[weblacky]

you either have an incomplete install CDROM image OR have a version of IRIX that PREDATES the Octanes introduction/creation to market.  You're literally missing the "Kernel" for the CPU Version/Family!  So either too old and you didn't get a complete copy....BE AWARE that the fact that your MOUNT command had an error leads me to believe that you don't actually have an image of the CROM you more have just the files from the EFS partition on the CDROM.  You need a LITERAL "DD image" of the CD...not just the "readable files" from mounting the CD under Linux and copying from EFS.  That isn't everything!

Irix install CDROMs are like every other UNIX install Disc!  They are actually formatted as if they were a hard drive with a 512 byte sector. They have the same partitions a hard drive would have. Irix has files stored on other partitions than the main EFI!  The CD image should at least have three partitions I think, it could have more. The entire thing is an emulation because it's easier for the firmware to read the CD as if it was a hard drive then to actually read the CDROM file systems of the day.  512-byte block Mode on older optical drives was designed for this exact purpose, that's why it's a non-standard feature in optical drives and pretty much nonexistent today.

So since I know the Octane was released BEFORE Irix 6.5.0...and you're sure you have 6.5 files then you have an incomplete CD image.  The mount command not detecting the partition #7 on the CD image validates that assumption for me.