Jerome Fine replies: While I agree it will be a great challenge to get the backplane working, you will probably was to use a 22 bit backplane so you can have more than 1/4 Meg of memory. That assumes that the original backplane was 18 bits to start with. However, I would suspect that many, if not most, 11/03 systems may have had the leads for 22 bit addresses used for power since I suspect that the 11/03 used some of those 22 bit leads in that manner. I am not sure I said this correctly, but please exercise extreme caution if you intend to put an 11/73 into an 11/03 backplane. As a somewhat more practical suggestion, I doubt that a BA23 box would be all that expensive and it would be much better suited to an 11/73 of any kind and is already a 22 bit backplane. Any of the other boards you rescue but not all. If I remember correctly, some early versions of the DLV11-J (M8049) were not able to handle 22 bit addresses. Also, which OS do you intend to run? Will you want it to be Y2K compatible? Sincerely yours, Jerome Fine Year 2000 Solutions for the RT-11 Operating System and Applications (Sources not always required)