Don't use a version of the system BIOS before version 4.03 to boot the Solaris software.
The special files that are created on an Intelligent SCSI Subsystem (ISS) are described in the iss(7D) man page.
Regardless of the number of devices on the ISS controller, a maximum of eight disk devices (physical or logical) are shown by the realmode driver when installing the Solaris software, which limits the number of drives that can be used for booting.