Since early 2016, the SGI TechPubs archive is no longer available at SGI. The backup location is at https://techpubs.jurassic.nl/.
(Related forum post: http://forums.nekochan.net/viewtopic.php?f=6&t=16730750)
Another way to access the old SGI documentation is to take their old links and visit them in the Archive.org's Wayback Machine.
Another way to find the required documentation is to search in http://manx.classiccmp.org/mirror/techpubs.sgi.com/.