Progressed a little further: [1] The 'ufs' command was a variation on the 'nfs' command. The man page that Noel provided for nfs includes the paragraph: "There is a command /usr/usg/tom/ufs which transfers files to the USG Unix systems. The option letter 7 for the 11/70 or 4 for the 11/45 should be used. Otherwise 'ufs' is similar to 'nfs'." This means there must have been a Unix based File Store (server). Does anybody have a suggestion who 'tom' at USG might have been? [2] The V5 man pages in the archive have a man page for 'npr', in section VI. It says: NAME npr - print file on Spider line-printer SYNOPSIS npr file … DESCRIPTION Npr prints files on the line, printer in the Spider room, sending them over the Spider loop. If there are no arguments, the standard input is read and submitted. Thus npr may be used as a filter. FILES /dev/tiu/d2 tiu to loop It suggests that the printer was hooked up to the Spider switch and that channel 2 was hardcoded to it. [3] Upon closer inspection, the tiu.c driver is a character mode device, the use of disk buffers and a strategy() routine had me confused. It is just a reflection of the fact that it uses DMA hardware. The code for tiu.c in NSYS/V4 is rather different from the code in the SRI-NOSC tree: thinking on how to select channels seems to have changed in between these two versions. [4] Also I found the below post that mentions the snstat() call: http://minnie.tuhs.org/pipermail/tuhs/2015-December/006286.html The object code for snstat() is in libc.a in the dmr's V5 image. Reconstructed, the source code is here: http://chiselapp.com/user/pnr/repository/Spider/artifact/a93175746bd9f94f In short, snstat() is a modified stty call, an evolution in the direction of the later ioctl() system call. No progress as yet on the early history of 'alarm()'. Paul