VAX 4000-100 QBUS cables

I don't know much about Vaxen, but I think the early desktop ones all had a QBUS. I'm not sure if it was ever used for memory access; I know some used it as an I/O bus (to take advantage of all the existing QBUS I/O devices), and used an 'over-the-back' cable system for the memory bus. 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. There are a whole bunch of different card and variants thereof for this, with and without termination resistors, etc; the M9400/M9401 pair are for Q18 (which you won't want, I'd be pretty sure), and the M9405/M9405 for Q22. One set I know of is an M9404/M9405-YB. There's a fair amount of discussion of multi-segment QBUS systems in the QBUS PDP-11 processor/etc manuals, as far as the termination, etc goes. As to finding a set, there are some available on eBait at the moment for a not wholly unreasonable amount of money. Noel