[robespierre]

If you read the man page for mtio(7) and tar(1), they discuss how IRIX's default tape device is byte-swapped. This is historical, for compatibility with the IRIS 2000 which had a byte-swapped tape interface.
By specifying the non-swapped device, /dev/tapens (for example, by using the "f" option to tar), you can get the alternative behavior which may be more compatible with other systems like Sun.

The tar(1) page also gives a pipeline using dd(1) with the conv=swab option, as an alternative way to reverse byte-swapping.

Code:

tar tf /dev/tapens