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.)
KA11 modifications
An M138 FLIP CHIP (octal three-input NAND gates) is also plugged into the KA11 backplane (in slot B08, otherwise unused), to provide additional gates.
The following list of wiring changes on the KA11 backplane is drawn from print 7605961-0-11, "KA11 Mods For Use With KT11-B". All wires are listed as being 30 AWG. (Note: This print reproduced poorly, so there may be transcription errors (e.g. '8' for '3', etc.)
Wires removed
| From | To | Signal | Colour |
|---|---|---|---|
| B02T2 | F08U2 | K13-3 B MSYN H | Orange |
| D12C2 | D12S1 | GND 12 | |
| E04K1 | E07P2 | K10-4 CLKT H | |
| E03F1 | E04L1 | K?-2 SCLK L | |
| D11B1 | C06J1 | K10-3 ODD ADRS ERR L | |
| C06J1 | D02N1 | K10-3 ODD ADRS ERR L | |
| D12S1 | D12T1 | GND 12 | Brown |
Wires added
All added wires are listed as Orange. This list had previously been checked, and annotated by hand in ink; those annotations are given here. All entries with no annotation given have a hand-written check-mark in ink.
| From | To | Signal | Comment |
|---|---|---|---|
| E03F1 | F06H1 | K1-2 SCLK L | |
| Dx2C2 | D12T1 | GND 12 | None |
| D11B1 | D02N1 | K10-3 ODD ADDRS ERR L | None |
| xx | yy | K10-2 ODD ADDRS ERR L | |
| xx | yy | K10-2 ODD ADDRS ERR L | |
| xx | yy | K10-2 ODD ADDRS ERR L | |
| xx | yy | B08D1 | |
| xx | yy | B08D1 | |
| xx | yy | K1-2 SCLK L | E04L1 - B08M1 |
| xx | yy | B08J1 | |
| xx | yy | B08J1 | |
| xx | yy | B08N1 | |
| xx | yy | K10-2 CLKT H | |
| xx | yy | K10-2 CLKT H | |
| xx | yy | K10-2 CLKT H | |
| xx | yy | E08U1 | |
| xx | yy | E08U1 | |
| xx | yy | D18 - PGC 04 (1) H | |
| xx | yy | D18 - PGC 04 (1) H | |
| xx | yy | D18 - PGC 04 (1) H | |
| xx | yy | B08H2 | |
| xx | yy | B08H2 | |
| xx | yy | B08H2 | |
| xx | yy | B08H2 | |
| xx | yy | K1-4 SERVICE H | |
| xx | yy | K1-3 ISR (3+7) H | None |
| xx | yy | B08S2 | |
| xx | yy | B08S2 | |
| xx | yy | B08S2 | |
| xx | yy | K12-3 TRAPS | B02C1 - B08P2 |
| xx | yy | K1-3 B DEST (0) H | |
| xx | yy | K1-4 B SOURCE (1) H | B09H1 - F11M2 |
| xx | yy | K1-3 ISR 12 L | |
| xx | yy | K1-3 ISR 7 L | |
| xx | yy | K10-4 RTI H | |
| xx | yy | K10-2 JSR H | |
| xx | yy | D18 CLK NPR H | |
| xx | yy | K10-3 RTS | B09D2 - E11T2 |
| xx | yy | K1-4 SERVICE L | |
| xx | yy | K13-3 TIME OUT (0) H | |
| xx | yy | K1-4 FETCH (0) H | |
| xx | yy | K10-2 TRAP L | |
| xx | yy | K13-3 -(ST+SR) H | D06D2 - B11T2 |
| xx | yy | D18 FORCE TIMEOUT H | |
| xx | yy | B08V1 | |
| xx | yy | K2-3 CLR PTR L | None |
| xx | yy | K2-3 PERIF REL L | None |
| xx | yy | DEVICE 2+3 BG06 | |
| xx | yy | K1-2 R/W2 H | |
| xx | yy | B08M2 | |
| F02J1 | C06V1 | - | Unlisted (Not in original table; added by hand) |
| B09H1 | F11M2 | - |
