Not quite; it does _mostly_ 'do its thing' over the UNIBUS, but there are also two special lines carried across the DD11-P backplane to the CPU, 'Halt Request' and 'Halt Grant' (which is why it has to be in the same backplane as the CPU); more here: http://gunkies.org/wiki/KY11-LB_Programmer%27s_Console I'm not sure exactly what you mean by 'demux', but... the interface between the board and console is i) 3 bits of digit, and ii) 6 individual select lines. Code in the micro on the M7859 sends one digit at a time down the 3 'digit' lines, along with the appropriate 'select' line. Well, I haven't looked at the M9312 ROM code, but if it's anything like the M9301 code (which I have dumped and disassembled), looping in the ROM at 173066 is not necessarily bad. There is a listing of some of the ROM code on BitSavers: http://bitsavers.trailing-edge.com/pdf/dec/unibus/K-SP-M9312-0-5_Aug78.pdf but it doesn't seem to cover the stuff at 173000 (which is where the CPU starts running on power-on) - or maybe I just didn't study the listings carefully enough. Depends on the switch settings on the M9312. If it's set to boot, if the device is there, yes; otherwise it would get a NXM fault. If it's set to go into the console mode, it's probably trying to read characters (commands) Noel