The 11/45 has booted an OS for the first time since I got it. RT11 came right up. Interrupts are working. Awesome :) That's actually very satisfying because the machine was in very rough shape when I got it. After fixing the power supply (which was a new problem, unrelated to the previous interrupt issue I think), I started growing the configuration back to where I wanted it to be in little increments... like adding the BA11K back in (with nothing in it, just the 930). Then putting in the M9312, Then adding in the unibus memory, RL controller, dropping the core out of the picture, etc.... and testing between each small step. It got back to the full config and still interrupts are working. So, unfortunately I'm not sure what actually fixed the problem which is a little unsettling. But it was a big thrill to see the RT11 prompt :) That being said, I am using a borrowed set of cpu boards. Over the next few sessions I plan to start adding my boards back in one at a time and I'm betting some of them won't work so I'll still be looking for help to repair those (and that will also help me understand the machine better). Note that the interrupt problem occured with the same borrowed cpu boards, but now it's gone. Odd. Another oddity reared it's head. The system was very stable with just the RL controller. I then installed an RX02 (M8256) controller (and removed the NPR jumper for that slot). I turned on the system but left the RL02 turned off. The RX02 worked perfectly. Then I turned on the RL02. It powered up ok (no fault) but when I spin it up I got a fault light. It is not the drive, nor is it the pack. If I shut everything down and leave the RX02 drive powered off (but controller still installed), the RL02 will come up fine and not fault. So there is apparently something that the RL controller doesn't like about the RX02 controller? The NPR jumper is removed for the two slots where the RL and RX controllers are, but definitely present in all other slots. I'm also soliciting advice on memory configuration. The processor has 16Kw core in the system chassis. I don't own any MOS/Bipolar. I have two unibus 64Kw memory boards (M7891 I think it is). My plan was to run the system with one 64Kw unibus board, hold the other for spare, and leave the core disconnected. I know I can run RT11 ok in 64kw. But based on requirements for other things like RSTS, etc... am I better off leaving the 16kw of core connected? In other words, for most DEC OS's on the /45 am I going to have trouble with 64kw but not 80kw? If it won't make a difference in what I can run I'll probably just leave the core disconnected. Thoughts? Thanks! Jay West