Support for the EIS was optional, with the KE11-E Extended Instruction Set, a hex card. There was also optional floating point hardware, the KE11-F Floating Instruction Set, a quad card; it was not the full FP11 Floating Point, but the minimal FIS floating point.
Memory management support was also optional, with the KT11-D Memory Management, another hex card; it too was not the full PDP-11 Memory Management, but the simplified subset. Other CPU options included the KJ11-A Stack Limit Register, and the KW11-L Line Time Clock (the latter being a standard option across a number of PDP-11 CPUs).
The basic KD11-A was contained on four hex cards:
- M7231 - Data Paths
- M7233 - IR Decode
- M7234 - Timing
- M7235 - Status
and one quad card:
- M7232 - μword
The Berg connectors on the M7232 carry the microcode bus to the optional KE11-E EIS card; note also the metal edge handle on this card, even though it is only a quad card; it and the KE11-F FIS card are the only non-QBUS quad cards known to have such a handle.
All of them plugged into a wire-wrapped custom 9-slot backplane dual system unit. The optional KE11-E Extended Instruction Set, KE11-F Floating Instruction Set, and KT11-D Memory Management option cards all plugged into pre-wired slots in this backplane, as did the KJ11-A Stack Limit Register and the KW11-L Line Time Clock. This left one unused slot, which was wired as a UNIBUS SPC slot; that slot also contained the 'UNIBUS out'.
Board locations are:
|1||M7239 FIS||KM11-A (KT, KE)||KM11-A (KD)|
|3||M7232 u Word||KJ11-A||KW11-L|
|4||M7231 Data Path|
|5||M7233 IR Decode|