KA11 changes for the KT11-B
The KT11-B Paging Option for the PDP-11/20 involves some modifications to the KA11 CPU. Those changes are documented in a DEC print set, 7605961-0, "Central Processor for KT11-B".
Alas, there's only one known set of these prints for the KT11-B changes to the KA11 - and that set is missing a page: "PC Board Modifications", D-AP-7605961-0-10.
Luckily, there is probably just duplicate information elsewhere (including a hand-modified set of KA11 prints, showing the changes to suppport the KT11-B) to allow it to be reproduced.
Print set
The following prints are included in the "Central Processor for KT11-B" set:
| Drawing | Sheets | Title |
|---|---|---|
| D-CS-7605961-0-3 | 3 | State Control - M727 K2 |
| D-CS-7605961-0-4 | 3 | Priority - M824 K3 |
| D-CS-7605961-0-5 | 5 | Bus Interface & Instruction Register - M725 K9 |
| D-CS-7605961-0-6 | 4 | Instruction Register Decode - M726 K10 |
| D-CS-7605961-0-7 | 3 | Flag Control - M822 K12 |
| D-CS-7605961-0-8 | 4 | Bus & Console Control - M724 K13 |
KA/KT Interface
The KA11 and KT11-B are connected by a single cable which carries specific signals, as well as the UNIBUS. On the KT11 end, it plugs into slot D12, and on the KA11 end, into slot B09. The cable pinout is:
| Pin | Source | Signal | ! Pin | Source | Signal |
|---|---|---|---|---|---|
| A1 | - | Ground | A2 | ? | xx |
| B1 | KA11 | Odd address error | B2 | ? | xx |
| C1 | - | Ground | C2 | - | Ground |
| D1 | KT11 | PGC 04 | D2 | KA11 | RTS |
| E1 | KA11 | DEST | E2 | KA11 | CLKT |
| F1 | - | Ground | F2 | - | Ground |
| H1 | KA11 | SOURCE | H2 | KA11 | -TRAPS |
| J1 | KA11 | ISR 12 | J2 | - | Ground |
| K1 | - | Ground | K2 | KA11 | SERVICE |
| L1 | KA11 | ISR 7 | L2 | - | Ground |
| M1 | KA11 | -RTI | M2 | KA11 | TIME OUT |
| N1 | - | Ground | N2 | - | Ground |
| P1 | KA11 | JSR | P2 | KA11 | FETCH |
| R1 | - | Ground | R2 | - | Ground |
| S1 | KT11 | CLK NPR | S2 | KA11 | TRAP |
| T1 | - | Ground | T2 | KA11 | [ST+SR] K13-3 |
| U1 | ? | xx | U2 | ? | Ground |
| V1 | ? | xx | V2 | KT11 | Force timeout |
(Signals partially in lower case are not formal names from the prints, but give a sense of what the signal does.)
