H9273 backplane

The H9273 backplane is a 9-slot Q/CD QBUS backplane, the standard backplane in the BA11-N mounting box. It could hold quad-sized cards.

It was a Q18 backplane, but it is relatively easy to upgrade it to Q22.

The manual says the BA11-N was for PDP-11/03L's, but the LSI-11 used in that machine was only Q16 capable, making the Q18 backplane superfluous, like that in the BA11-M mounting box. Once the PDP-11/23 appeared, BA11-N's could be used with it (and perhaps the BA11-N was looking forward to this machine) - but after the -A revision of the /23's KDF11-A CPU (Q18 only), later revisions really were better off with a Q22 backplane, as in the uprated BA11-S mounting box.

Since it was a Q/CD backplane, dual-width QBUS cards could only be placed in the left-hand slots, and quad QBUS-only cards had to not use any pins on the right-hand C/D connectors. (The only DEC card with a problem with this seems to have been the MMV11-A.)

External links

• BA11-N mounting box user's guide (EK-BA11N-UG-001) - the H9273 is covered on pp. 10-13
• PDP11/23 Field Maintenance Print Set (MP00740) - The H9273 is covered in the BA11-N Field Maintenance Print Set (MP00487) on pp. 41-51