In that case, I would assume that the PDP-11/84 backplane is wired so that the PMI memory is activated correctly WHEN the CPU is in slot 1 and the first memory board is in slot 2. Note that I am repeating what you just stated. The reason that I have stated this for the PDP-11/84 is because for the PDP-11/83 (usually in a BA23 or a BA123), the backplane is wired so that the PMI memory is activated correctly WHEN the first memory board is in slot 1 and the CPU follows the memory boards. I made another err. I meant the KDJ11-BD board or the M8190-AC. Since I will never have an opportunity to ever use a PDP-11/84, it will never be possible to check my question. HOWEVER, NOTE that the identical CPU board, KDJ11-BF (M8190-AE), is used in BOTH the PDP-11/83 and the PDP-11/84. The KDJ11-BD is the M8190-AC, a quad board (if I remember correctly). Although the KDJ11-AC has a 15 MHz crystal, when used in the correct position in a BA23 box, namely AFTER the PMI memory, the KDJ11-BD is reported as a PDP-11/83 by the RESORC.SAV program and the speed of the system is about 20% faster than when the PMI memory is placed into the ABCD slots AFTER the CPU at which point RESORC.SAV reports the CPU as the PDP-11/73B. That is why it seems reasonable to hope that the PDP-11/84 can also use the KDJ11-BD instead of the KDJ11-BF, except that it would then run about 10% to 15% slower. Jerome Fine