PDP 11/40 Unibus termination query...

[Josh Dersch]

Hey all --

I'm one step closer to bringing my 11/40 back to life -- the front panel 
is now responding and I can examine and deposit memory.

But the machine is only responsive without the Unibus terminator (an 
M9302) installed.  If it's installed, the front panel is basically hung 
-- toggling "Start" causes a brief flurry of activity, but that's the 
only thing that causes any response.

Without the terminator installed, the front panel more or less works, I 
can examine and deposit memory, load the address register, etc... but I 
can't get any toggled in code to run, obviously -- it traps to the bus 
error vector at 00004. 

(There's also an odd issue, which I doubt is related, but 
Examining/Depositing does not correctly increment the address -- 
starting from 0, it's "0, 2, 6, 12, 16, 22, 26..." and if I start at 1 
it's "1, 3, 7, 13, 17, 23, 27...")

I currently have the CPU boards + MMU option installed in the correct 
order with a SLU card in the SPC slot, and an M981 connecting to a 
4-slot Unibus backplane with a single 64K MOS memory card (M7891) in 
slot 2 -- all other slots have grant continuity cards installed.  The 
Unibus terminator is installed in the last slot.

Any ideas? 

Thanks as always,
Josh