So I flipped the restart switch on the CPU, answered "Y" to "Start?" and got a message "Please boot from system disk". I have one other disk pack that is known to have come from a PDP-11, so I put it in the drive - lo and behold, "Booting up XXDP-XM Extended Monitor" followed by ... "V2.4, Rev. E1, booted from DL0, 124Kw memory, Non-Unibus system, restart address 152000, type H for help". Looks like I now have a working PDP-11 :) The pack has 727 files on it whose names are meaningless (to me anyway). XXDPXM.SYS etc. is obvious but there are hundreds of files from A to Z with names like "VKMHA0.BIN", "ZAFAC0.BIC" and some .LIB and .OBJ files too. What on earth do I have here? Is it something that anyone would be interested in copying?