You wrote.... The RX02 controller is first on the bus (in the expansion cabinet). The only I/O card in the cpu is the console board. This is cabled to the BA11-K expansion box. Slot 1AB is the unibus in cable, slot 1CF is the M8256 controller. Slot 2AF is the RX02 controller (M7266 I think). Then slot 3AF is my MS11 unibus memory board (M7891 I think). The rest of the slots have grants up to and including the last slot. The last slot has the M9312 in AB. I put the RX02 controller in 1CF so that it wasn't a wasted quad slot. So yes, if I change the NPR jumpers accordingly and move the cards around I could put the RX02 controller after the RL02 controller and see if it *HIDES* the problem. But I'd still like to fix it. On another note... this RX02 controller was in a 11/44 recently, and the SDI controller came after it (in a later system unit). So if it was screwing up the bus for following cards I would THINK I would have seen it in the UDA50 controller. But who knows :) Jay