but an RM80 will work fine off of the RB730 controller. Not exactly - I knew that the R80, RA80 and RM80 are all the same drive except for the personality modules. Certainly the HDAs are all the same. The R80 essentially has no personality the RB730 does all the work. I guess the RM80 must have the MASSBUS controller in a separate box? So the actual drive is like the 730 it has no personality module inside? My first home machine was an 11/725, to which I added an RB730 controller , and I used it with an RM80 for a number of years, until power problems killed a bunch of boards in it. Do you still have it? I have some spare boards (or alternative, I also have a 725 that needs a new chassis :-) Bob