Hi Well lots fun with the 11/94 project. In fact its become an 11/84 and 11/94 project. After following Sherlock Holmes advice "when you have eliminated everything else.Whats left however unlikely is the answer" I discovered the RX211 needed to be in CDEF and not ABCD. Why did I not know that? Well I can only put it down to the fact all of the UNIBUS options I ever worked with were hex modules. Next fascinating fact. You can switch between being an 11/84 and an 11/94. Although one box has three Qbus slots and the other (11/84) has four. If you put an 11/84 CPU in slot 1 and a MSV11-J (PMI) in 2 or 3 it does its startup tests and goes into the monitor screen. If you try to boot the RX02 in 11/84 mode you get (the drive does get accessed - there's a nice healthy clonk) Trying DY0 Error 101 Unexpected trap to location 114 See troubleshooting documentation Updated PC 173260 PCR Page = 62 Program listing address = 062260 R0 = 000000 R1 = 177170 R2 = 042131 R3 = 000000 R4 = 024000 R5 = 000000 R6 = 172276 R7 = 001600 In 11/94 mode it stops at the same point but does not give the error message. Comments gentlemen please Rod Smallwood