BA11-N mounting box

The BA11-N mounting box was the first mounting box used for the PDP-11/23 from DEC. It included an H786 power supply, and an H9273-A 9-slot Q/CD backplane, which could hold quad-sized cards.

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 H9273-A was a Q18 backplane, but it is relatively easy to upgrade it to Q22.

It was available both with a front panel (with 'Boot', 'Halt' and 'LTC On' switches), and with a blank front panel.

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.

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).