Start with the SGI Video BreakOut Box User's Guide:
http://techpubs.sgi.com/library/manuals ... index.html
The vbob software is included in the DMedia DM2/DM3 software distribution. If you don't have it I think it's on Ian Mapleson's 'depot' resource and/or Nekochan FTP. It may even still be on SupportFolio
Keep in mind that the whole DMedia package can do two different things: video I/O to decks, cameras, (HD)SDI video monitors etc. using the DM2/DM3 + vbob, and GVO (graphics-to-video). GVO is optional and requires a DM5 in the vbob. You need DVI to connect to the DM5 so an Octane V12 needs a DCD. The vbob put the corresponding (HD)SDI signal on the BNCs, and you can attach the (graphics) monitor to the DM5 output.
You can telnet the vbob but I think it's only useful to run diagnostics on the thing or maybe recover from a bad flash. I normally do not have a serial cable connected to the vbob. You cannot telnet from the PROM.