The report I have is: "SPIDER-a data communication experiment", Tech Report 23 , Bell Lab, 1974. I did not find it online, but it may be out there somewhere. I think it can be public now, but doing some checks. Many thanks! There is some puzzling stuff in there that I'd like to figure out, but that is easier to discuss once the report is online. Also, it turns out that the TIU driver was in Warren's repo all along: http://minnie.tuhs.org/cgi-bin/utree.pl?file=V4/nsys/dmr/tdir/tiu.c http://minnie.tuhs.org/cgi-bin/utree.pl?file=V4/man/man4/tiu.4 It's fun to read that the V4 man page says "The precise nature of the UNIX interface has not been defined yet." and Noel's version says: "The precise nature of the UNIX interface is defined elsewhere." (yet the dates are the same!). Some things are surprising (to me, at least): First of all, opening a connection to the File Store is a single open on data channel 1: http://chiselapp.com/user/pnr/repository/Spider/artifact/854a591c0e7a3a54?l… I would expected the code to first have sent a connection request to the switch on control channel 1. Perhaps the File Store was an integral part of the switch/router (a Tempo minicomputer ftp://bitsavers.informatik.uni-stuttgart.de/pdf/tempoComputers/TEMPO-1_ad_Nov69.pdf) with channel 1 functionality hardwired. Next, the code has a hackish form of non-blocking I/O: http://chiselapp.com/user/pnr/repository/Spider/artifact/55ee75831bd98d6c?l… I'm puzzled about the alarm() sys call. That did not exist in 1973 -- or did it only exist in Bell Labs private builds? The code calls snstat(), for instance here: http://chiselapp.com/user/pnr/repository/Spider/artifact/55ee75831bd98d6c?l… That seems to be a sys call to here: http://chiselapp.com/user/pnr/repository/Spider/artifact/2c7d65073a7cb0a5?l… Could that be the tiu sys call (#45) in the sysent.c table for V4-V6?