General Question about UNIBUS backplanes

Strictly the core backplanes are not Unibus backplanes. They have Unibus In and Out connectors, but the slots are wired for the core memory board, not Unibus boards (like SPCs -- Small Peripheral Controllers -- which is what you serial port is). No. In fact in most cases it is wrong to put grant continuity cards in there. However in a lot of cases a special backplane (like your core memory one) will have some spare slots (perhaps the core memory doesn't take up all 9 slots). And DEC often (but not always) wired those so you could put SPCs in there. In which case you will need grant continuity cards in those slots if you have nothing else in them. See above. The slots for the core memory and controller cards are special and can only take those cards. But you might have normal SPC slots on the same backplane. You need to find the 'module utilisation chart' for that core memory backplane. Be warned that DEC normally drew these looking at the _wire side_ of the backplane, not the side where the PCBs go! -tony