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It's worth remembering the following guide if you're identifying PDP11 or 
VAX boards : 

Hex height, metal handles -> Unibus (or special PDP11 CPU board)
Quad height, metal handles -> Q-bus
Quad height, plastic handles -> Unibus
Dual height, plastic handles -> Qbus (or maybe a very early Unibus option 
to use with an M105 and M782).

Bus priority jumper (a little PCB about 1"*3/4" on a 16 pin header) -> 
Unibus.

Yes, there are a lot of exceptions, but it works a lot of the time (and 
it's easy to remember)

Omnibus (PDP8/e, etc) boards are often also quad height with plastic 
handles. A couple of tricks to spot those : 

'Top' edge connectors -> Omnibus
Plastic spacers between handles and PCB -> Omnibus
Connectors on the 'wrong' edge -> Omnibus -- If you hold the board, 
component side up, edge connectors on the left (and handles on the 
right), then a header plug on the 'top' edge -> Unibus, one on the bottom 
edge -> Omnibus.

ard_@_p850ug1.demon.co.uk (Tony Duell)

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