Combination and Orientation of RQDX boards in one PDP-11/23 PLUS

SPC spedraja at
Sun Jun 21 14:08:04 CDT 2009

Well, for my surprise I've discovered a set of three boards in a lot that
received from the US some months ago and I couldn't poen until now. It comes
with three RQDX boards, more exactly:

* 7555
* 7513
* RQDX distribution signal

As far as I can imagine it appears that they were used in one PDP QBUS
system in the order, from up to down in the order of the previous list, with
one ribbon cable from the RQDX3 to the 7513 J1 (?) connector, and another
one from the J2 (?) to the RQDX distribution board. Exists another connector
(J3 ?) in the 7513 that appears to point to one external connector that I
saw in one BA23.

Finally, the RQDX comes with MFM cables but too with one standard floppy PC
cable. I have some doubts with this last matter:

* Is used this crossed floppy cable in DEC systems too (as in PeeCees) or
it's used other kind of cables ?
* I have a couple of RX33. Must I use TWO cables (one per floppy unit) ?
* Same question with the MFM disks
* What is the orientation of the RQDX ? I imagine it with the connectors
side turn down because turning it up would be a problem with the previous
board in the BA11-SB

Can this be possible ?

By the way, these questions connect with your last comments about the matter
in the list, which is being an open book of knowledge for a newbie as me.

Thanks all. Regards.

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