Small DEC QBUS backplane

Glen Slick glen.slick at
Sat Jan 30 17:08:42 CST 2021

On Sat, Jan 30, 2021 at 2:20 PM Nigel Johnson via cctalk
<cctalk at> wrote:
> Yes the BA11S would be too big. Can't see why not for the 11/03 chassis.
> I used to make a good living upgrading 1/03 chasses with four extra bits
> for the 11/23/73  (Hmm, where is my old stock of W933 bus strip!)
> Always works except in the MINC laboratory system, which used those four
> pins for module identification.
> Since all the memory is on-board with the 11/93 I don't think it would
> make a difference unless DMA used, and I don't plan to go that far!  I
> could always wire-wrap them.

The KDJ11-E 11/93 has PMI signals on the CD connectors, so you need a
Q/CD backplane, such as the 18-bit 4x9 H9273, the 22-bit 4x9 H9276, or
the 22-bit 4x8 H9278 (BA23 backplane).

The 4x4 H9270 is a Q/Q backplane, so that would cause a conflict with
the PMI signals on the CD connectors of the KDJ11-E 11/93.

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