Reading the replies, not from the screen, but printed, I notice a comment from Tony. This could be important! That's an eye-opener for me! I thought that the DL11 would short CA1 to CB1. I guess that some cards that do not use DMA (NPR) short these 2 pins and some *do not*. Since the machine was originally with a remote console, (hard lesson: DO take notes on any action you do to a PDP-11, if you do: make better/more elaborate ones), I think that there was no DL11 in it, but the Unibus serial remote console M8255 was in slot #40. I swapped the M8255 for an M7856. Now, if the M8255 *does* bridge/use NPR ... I will check this evening of course, no matter what pops up! I will do the other tests anyway, and make notes! They will be very useful for future reference. Again, thanks all so far, - Henk.