VAX 4000-100 QBUS cables

Maciej W. Rozycki macro at
Mon Nov 28 09:14:57 CST 2016

On Mon, 28 Nov 2016, Noel Chiappa wrote:

>     > However, I don't have the cables necessary to attach a QBUS expansion.
>     > Does anyone have a set? What do they even look like?
> They are a pair of boards connected with a pair of 50-pin cables. The boards
> are different on each end, because the QBUS does not have in/out connectors
> which separate from device slots, like the UNIBUS; it only has regular QBUS
> slots, and those have grant in on different pin from grant out. So on the card
> at the end of one backplane, the grant line is connected to the 'grant in'
> pin, and on the other card, to the 'grant out' pin.

 FYI, the VAX 4000-100/105/106 (KA52/KA54/KA54) systems have no backplane 
of any kind and do not use Q-bus internally, except for the CQBIC (CVAX to 
Q22-Bus Interface Chip) ASIC directly bridging one of the NCA (NDAL to 
CDAL Adapter, or the north bridge in modern speak) ASIC's CP peripheral 
buses to a mainboard Q-bus connector further wired with an internal cable 
assembly to the pair of external connectors mounted on the backside of the 

> As to finding a set, there are some available on eBait at the moment for a
> not wholly unreasonable amount of money.

 For the record they are DEC P/N BC04V-09 (17-02048-01), though the photos 
with the only listing I could find indicate quite a sorry state of the 
cables offered I'm afraid.


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