Ok, finally stopped being distracted by other shiny objects for long enough to do some more fiddling with the 11/40. And of course, instead of hooking up the logic analyzer, I decided to play around with the Console SLU/LTC board. Because I evidently don't follow suggestions well. But this has a good ending, sort of. Maybe. So the SLU was unresponsive no matter what I did. Tried it at 9600 baud, no go. Dialed it down to 300, no dice. Checked the continuity of the dip switches, of which there are approximately 500. No problems there. Checked, and double-checked the wiring on the serial cable I built. No go. Stole the cable from my 8/e... still no good. So I moved it out of the 9th slot on the processor backplane and into the first slot on Unibus backplane. (And put a grant card in the 9th slot...) And hey, it works. Toggled in a short "echo" program and what I type on the terminal keyboard is echoed back, at a blistering 300 baud.

So... clearly there's something wrong with the SPC slot on the processor backplane. A couple more questions: 1) Is the NPG grant on the unibus slot on the processor backplane (slot 9) supposed to be connected to the NPG grants on the Unibus expansion? That is -- right now if I set my DMM to continuity mode and put one probe on CA1 on the first slot of the unibus expansion, and the other on CB1 on the last slot of the unibus expansion, since all NPG grant jumpers are in place, the DMM shows the circuit as closed. This is as I'd expect. However, if I move the probe from CA1 on the first slot of the expansion to CA1 on slot 9 of the processor backplane, the circuit is then open. I'm guessing this is not correct. (There is currently an NPG jumper installed on slot 9.)