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.
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 KE11-E EIS card; note also the metal 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 with such a handle.
All of them plugged into a wire-wrapped custom backplane dual system unit. The 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.
- What Makes A PDP-11/35 Tick? - List of chips in the KD11-A