This is not a question just a heads up to others. I was recently in contact with someone who needed helping retrieving some old files from a cpio archive created on IRIX. I decided to post a solution here because while there are similar threads
on various forums on the Internet they don't ever seem to have solutions (and I am not a member on those forums). My hope is that this thread will get picked up by the search engines and the next person who encounters such a problem will find his/her solution.
The summary of the issue is that cpio on IRIX supports extensions to the old binary cpio format that allows it to handle larger files and more device bits, when using the '-K' switch during archive creation. However these extensions are not supported by most other cpio implementations (e.g. GNU cpio and bsdcpio/libarchive). Attempting to extract files from a SGI/IRIX cpio archive that includes such extensions will result in errors (e.g. "premature end of file" with GNU cpio).
However the cpio and pax utilities provided by The Heirloom Toolchest
understand these extensions and will therefore be able to retrieve files from such archives.
As a side note the Heirloom cpio and pax utilities can also open cpio archives that use similar (but not identical) types of extensions used on Cray and SCO systems.
P.S. If anyone involved with libarchive and or GNU cpio ever happens to stumble across this it would be nice if you would consider adding support for these extensions as well (I am making the assumption that they are not overly complex) as it would no doubt help others since The Heirloom Toolchest (whilst very cool) is not widely known.