Brad Parker wrote: Jerome Fine replies: Since I have substituted an M8190-YB (KDJ11-BB) for a Quad PDP-11/23 board, I know it can be done. As for the M8192-YB (KDJ11-AB), it will probably work, but do NOT expect to be able to boot RT-11 as before since the PDP-11/23 CPU boot ROMs for the M8186 CPU have code which crashes a PDP-11/73. If my assumption that the original system uses the M8186 is incorrect, then you need to supply additional information. If you are willing to use ODT to enter a boot program, then you should be able to boot RT-11 as before. If your information about having an 18 bit backplane is correct, then you are probably not going to damage the M8192. But if you actually have only a 16 bit backplane which runs an LSI/11 CPU, there may be extra signals where the extra 6 address lines are located. In that case, it is likely that you may damage the M8186. Tony, can you help this fellow in that regard? Sincerely yours, Jerome Fine -- If you attempted to send a reply and the original e-mail address has been discontinued due a high volume of junk e-mail, then the semi-permanent e-mail address can be obtained by replacing the four characters preceding the 'at' with the four digits of the current year.