I was lucky enough to pickup a PDP-11/70 last week, thanks to the generosity of a fellow collector.
The racks
| The PDP-11/70 Maintenance and Installation Manual (EK-11070-MM-002) explains that the basic PDP-11/70 system components are located in a double cabinet as shown in Figure 1-1 of that manual. That figure is shown to the right. You can click on it for a larger version.
My system is similarly configured in two racks. The main difference being that in my system the CPU Mounting Box and Memory Frame are in the one rack, with the second rack housing the Unibus expansion box. Both cabinets are about 50% full. This leaves a reasonable amount of space to add some peripherals to each cabinet. Further H960-C cabinets can be added to accommodate additional memory or peripherals. |
 |
Here are some pictures of the racks (vertical):
… and more pictures (horizontal):
Main Processor Box
The standard decal showing the modules in a PDP-11/70 is shown below (this is Figure C-3 from the Maintenance and Installation Manual):
Figure 4-20 of the Maintenance and Installation Manual shows a more detailed view of the backplane, viewed from the wirewrap side:
Based on a quick check, my 11/70 seems to be pretty much complete.
This machine has the KB11-C CPU, as evidenced by the M8123 in Slot 9. The earlier KB11-B processor would have an M8133 in Slot 9.
There’s no floating-point option fitted to this 11/70.
The PDP-11/70 processor box has capacity for the following peripheral controllers:
- 4 x RH70 Massbus Controllers (each controller takes up 4 slots)
- 5 x SPC Slots
There are no RH70 Massbus Controllers installed in this 11/70.
The peripheral controllers actually installed in this 11/70 are:
- Emulex SC72 SMD controller (in the Massbus Controller C slots)
- RL11 RL01/RL02 Disk Drive Controller
- Emulex TC13 Tape Coupler (emulates TS11)
- DL11-W SLU & Real Time Clock
Here’s the full list of modules in the processor box:
| Slot | Part No. | Description |
|---|---|---|
| 1 (Rows E-F) |
M9312 | Unibus Terminator and Bootstrap Loader and Diagnostic |
| 2-5 | Empty | Floating Point Processor |
| 6 | M8130 | 11/70 Data Paths |
| 7 | M8131 | 11/70 General Registers and ALU Control |
| 8 | M8132 | 11/70 IR Decode and Condition Codes |
| 9 | M8123 | 11/70 ROM & ROM Control, FP11-C compatible |
| 10 | M8134 | 11/70 Processor Data and Unibus Registers |
| 11 | M8135 | Trap and Miscellaneous Control |
| 12 | M8136 | Unibus and Console Control |
| 13 (rows C-F) |
M8139 | Timing Generator |
| 14 | M8137 | System Address Paths |
| 15 | M8138 | System Status Registers |
| 16 | M8140 | System Descriptor / Console Cables |
| 17 | M8142 | Cache Control |
| 18 | M8143 | Address Memory |
| 19 | Empty | Not Used |
| 20 | M8144 | Data Memory |
| 21 | M8145 | Cache Data Paths |
| 22 | M8141 | Unibus Map |
| 23 | Empty | Not Used |
| 24-27 | Empty | RH70 Controller A – Spare |
| 28-31 | Empty | RH70 Controller B – Spare |
| 32 | SU7010406 | Emulex SC72 – C Board |
| 33 (Rows D-F) |
SU7010404 | Emulex SC72 – CST Board |
| 34 | SU7210403 | Emulex SC72 – B Board |
| 35 | SU7210401 | Emulex SC72 – A Board |
| 36-39 | Empty | RH70 Controller D – Spare |
| 40 | M7762 | SPC Slot – RL11 RL01/02 Disk Drive Controller |
| 41 | G7273 | SPC slot – Spare |
| 42 | TU131041 | SPC Slot – Emulex TC13 Tape Coupler (emulates TS11) |
| 43 | G7273 | SPC slot – Spare |
| 44 | M7856 | SPC slot – DL11-W SLU & Real Time Clock |
In addition:
- there are G727 grant continuation cards in 27D and 31D and 39D
- there are G7273 grant continuation cards in 41C-D and 43C-D
- there is an M9302 Unibus terminator in 44A-B
Memory Frame
The memory frame is mounted just above the CPU Mounting box.
This system is fitted with 512KB of memory (2 x M8728 256KB boards are fitted).
Figure 3-30 of the Manual shows the standard configuration of the Memory Frame:
The Memory Frame is populated as follows:
| Slot | Part No. | Description |
|---|---|---|
| 1 | Empty | Not Used |
| 2-8 | Empty | Storage Array (even) #14-#2 |
| 9 | M8728 | Storage Array #0: 256KB |
| 10 | M8161 | 0 Control B (Data & ECC) |
| 11 | M8160 | 0 Control A (Timing & Control) |
| 12 | Empty | Not Used |
| 13 | M8158 | Address Buffer |
| 14 | Empty | Not Used |
| 15 | M8164 | Data Buffer |
| 16 | M8160 | 1 Control A (Timing & Control) |
| 17 | M8161 | 1 Control B (Data & ECC) |
| 18 | M8728 | Storage Array #1: 256KB |
| 19-25 | Empty | Storage Array (odd) #3-#15 |
| 26 | Empty | Not Used |
Interestingly the same memory array boards (M8728) were also used in the VAX-11/780.
Expansion Unit
This Expansion Unit is a model H960-D. It has another sticker on it identifying it as a Box Type of “BA11-FE”.
It has a number of 4-slot and 9-slot back planes in it. I’m not sure yet which of these are “SPC” back planes, and which are special purpose back planes.
Here’s the list of the back planes and their contents:
Backplane 1 (4 slot):
| Slot | Part No. | Description |
|---|---|---|
| Slot 1 A-B | M9680 | “DR11-B Test Board” |
| Slot 1 C-F | M7219 | “Bus Interface” |
Slot 2: A-B empty, C: M208, D: M208, E-F: M7821
Slot 3: A: Small paddle board feeding power in, B: M205, C: M611, D: M611, E: M112, F: M112
Slot 4: A-B: M920 bridge, C-D: M7229, E: M116, F: M239
Backplane 2 (9 slot):
Slots 1 & 9: M920 bridge in A-B
Slots 2, 4, 6 & 8: G727A grant continuity card in D
Slots 3, 5 & 7: Completely empty (previous boards removed).
Backplane 3 (4 slot)
Slot 1: A-B: M920
Slot 2 & 3: D: G727A
Slot 4: Strange hex-width M7084, with small paddle-board above A-B bridged to M9202 in Backplane 4. Labelled “BUS REPEATER FOR PDP11” and “CSS MUNICH SSM 0235”. Also marked “DB11-H”. Has a “digital” sticker on Side 1.
Backplane 4 (9 Slot)
Slot 1: A-B: M9202 bridge from Backplane 3
Slots 2, 5, 8: M7814 (Multiplexer?) [Hex Width]
Slots 1, 3, 4, 6, 7 & 9 C: G727A
Slot 9 A-B: M920 to Backplane 5
Backplane 5
Slot1 A-B: M920 from Backplane 4
Slots 2, 4 & 6: M7814
Slots 1, 3, 5, 7, 8 & 9 D: G727A
Slot 9 A-B: M9302 terminator