[robespierre]

The internal document "hpc3.pdf" specifies that the HPC3 I/O chip can interface with two SCSI controllers, which can be either narrow (Western Digital WD33C93A or B) or wide (WD33C95 or Fujitsu MB86603).
The mezzanine board on the Challenge S has its own HPC3 with wide SCSI channels (WD33C95). So it's a mystery why the high-end Indigo2 was never upgraded to support wide SCSI if the capability already existed.

I know there are GIO64 ultra-wide controllers (I own one), but it just seems odd that SGI left the capability unused, even with the Impact 10000 in 1995. Weren't they at all afraid it would look anemic next to the Sun Ultra 1E?