General Question about UNIBUS backplanes

tony duell ard at
Sun May 22 11:33:02 CDT 2016

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).

> Basic Question #1
> Do I need grant cards in *every* empty slot of the core backplane,
> including the end slots with the M920's?

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.

> Basic Question #2
> Can you only use the core backplanes for core memory (assume yes), or are
> they capable of holding other types of cards temporarily? (yes/no/maybe)

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

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!


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