View source for BA11-N mounting box

The '''BA11-N mounting box''' was the a [[mounting box]] used for [[QBUS]] [[PDP-11]]'s from [[Digital Equipment Corporation|DEC]]. It included an [[H786 power supply]], and an [[H9273 backplane|H9273-A]] 9-slot [[QBUS#Backplanes|Q/CD]] [[backplane]], which could hold [[DEC card form factor|quad-sized]] cards.

The manual says the BA11-N was for [[PDP-11/03L]]'s, but the [[LSI-11]] used in that machine was only [[QBUS#Variable_address_size|Q16]] capable, making the Q18 H9273 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 up-rated [[BA11-S mounting box]].

Since the H9273 was a Q/[[CD interconnect|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 [[DEC edge connector contact identification|right-hand C/D connectors]]. (The only DEC card with a problem with this seems to have been the [[MMV11-A QBUS core memory|MMV11-A]].)

It was available both with a front panel with a bezel (with '[[bootstrap|Boot]]', '[[Halt]]' and '[[LTC]] On' switches, and power and run status indicators); and also with a blank front panel (for use as an expansion box).

It was a 5-1/4" tall mounting box, for the [[H960 rack|H960]] series of 19"-wide racks, one of the [[BA11 mounting boxes]]. The H960 racks provided 63" of vertical mounting space, divided into units of 10-1/2", which were further subdividable into a pair of 5-1/4" spaces. The 5-1/4" tall BA11-N mounting box was designed for these spaces.

For rack mounting purposes. it did not use external slides (as all the other BA11 mounting boxes did); instead, it was housed in an external 'skin' (termed a 'logic box cover' in DEC documentation, the base unit being called a 'logic box') into which it is slid; the cover would be bolted to the rack.

The backplane was mounted vertically, facing backward (unlike the BA11-M mounting box, where they had been facing forward). Cooling fans mounted on the side of the BA11-N passed air both over the boards, and through the power supply.

The BA11-N's dimensions were 5-1/4" high, 19" wide, and 22-3/4" deep, and it weighed 44 lbs (without any boards). The rack mounting was 26-3/4" long.

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==See also==

* [[BA11-M mounting box]]
* [[BA11-S mounting box]]

==Further reading==

* ''BA11-N Mounting Box Technical Manual'' (EK-BA11N-TM-001) - not available online
* ''BA11-N Mounting Box Illustrated Parts Breakdown'' (EK-BA11N-IP) - not available online

==External links==

* [http://www.bitsavers.org/pdf/dec/qbus/Digital_Microcomputer_Interfaces_Handbook_1980.pdf microcomputer interfaces handbook] - BA11-N is covered on pp. 74-82, 82-90 of the PDF
* [http://www.bitsavers.org/pdf/dec/qbus/Digital_Microcomputer_Products_Handbook_1985.pdf Microcomputer Products Handbook] - the BA11-M is covered in Chapter 54 (pp. 523-527 of the PDF)
* [http://www.bitsavers.org/pdf/dec/qbus/EK-BA11N-UG-001_BA11-N_Mounting_Box_Users_Guide_Jan78.pdf BA11-N mounting box user's guide] (EK-BA11N-UG-001)
* [http://www.bitsavers.org/pdf/dec/qbus/MP00740_1123_schem_Oct81.pdf PDP11/23 Field Maintenance Print Set] (MP00740) - Contains the BA11-N Field Maintenance Print Set (MP00487) on pp. 32-87)

[[Category: DEC Mounting Boxes]]
[[Category: QBUS Hardware]]