Difference between revisions of "BA11-N mounting box"

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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]] (which provided 22A of +5V, and 11A of +12V; although some sources give 15A and 8A respectively); and an H9273-A 9-slot [[QBUS#Backplane|Q/CD]] [[backplane]], which could hold [[DEC card form factor|quad-sized]] cards.
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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]] (which provided 22A of +5V, and 11A of +12V; although some sources give 15A and 8A respectively); and an H9273-A 9-slot [[QBUS#Backplanes|Q/CD]] [[backplane]], which could hold [[DEC card form factor|quad-sized]] cards.
  
 
The H9273-A was a [[QBUS#Variable_address_size|Q18]] backplane, but it is relatively easy to [[upgrading QBUS backplanes|upgrade it to Q22]].
 
The H9273-A was a [[QBUS#Variable_address_size|Q18]] backplane, but it is relatively easy to [[upgrading QBUS backplanes|upgrade it to Q22]].
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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]].
 
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 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]].)
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Since it 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 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).

Latest revision as of 16:54, 16 November 2019

The BA11-N mounting box was the a mounting box used for QBUS PDP-11's from DEC. It included an H786 power supply (which provided 22A of +5V, and 11A of +12V; although some sources give 15A and 8A respectively); and an H9273-A 9-slot Q/CD backplane, which could hold quad-sized cards.

The H9273-A 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.)

It was available both with a front panel with a bezel (with '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 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.