[weblacky]

Because several people have been gently trying to tell you that SGI CDs are almost never formatted in the ISO9660 standard to begin with. It wasn't saved in standard it was never written in.

People often mark the CD images as ISO to indicate the image is an image that can be burned. You could just as easily have put a .Img or .dd extension, but then people would keep asking questions on how to burn it and then you'd have to explain that when burning a whole/raw disk image that the file extension doesn't really matter and the extension doesn't indicate image format in this case, it's just a raw image. No one wants to keep explaining that so we still mark stuff as ISO so you'll at least try to burn the image, it will burn successfully, and then you'll only ask why it's unreadable, not how to burn it and why it's unreadable.

Many UNIX OSes, including Solaris, use CDs specially formatted in 512 byte blocks, often with a company-specific file system to accomplish this. While the reason for it originally was for a BOOTABLE/READABLE optical discs when in station firmware that makes the optical media/device appear similar to a normal 512-byte block hard drive to load the OS. But for non-bootable CDs they started doing the special formatting as well so they could use longer file names, symlinks, other special features not available in ISO9660 and so you had to have the correct computer to read it (back then) so it was unreadable in a pirating PC (you could copy it bit by bit though via duplication/imaging).

The ISO9660 file system was very basic, we've had improvements with extensions since then that didn't exist back then. But it was easier to format using their EFS file system to get more abilities while also making it more difficult for other platforms to read it.