This page shows the PDP-11/05 system I have at home.
DIGITAL introduced the PDP-11/05 and the PDP-11/10 as the first "inexpensive" PDP-11 in 1972.
My PDP-11/05 is housed in one H960 industrial 19" cabinet (from DIGITAL).
The cabinet also contains all the peripheral devices.
The following devices are in the rack (from top to bottom):
The PDP-11/05 is the OEM version of the PDP-11/10.
Hardware-wise the central processors are identical.
Both machines offer features not available on the earlier PDP-11/20, such as 4-level priority interrupt and multiple accumulators.
(The PDP-11/20 was the first 16-bit processor, April 1970).
Jumps within this page are the following:
Gé van der Veldt donated this PDP-11/05. He bought the 11/05 processor for 750 guilders from a dump store in
"Oude Pekela" (a city in the northern part of the Netherlands) in 1986.
The history of the processor before that date is not known. Gé added the Perkin-Elmer and the RK05 at a later time.
When Gé wanted to expand the system, DD11-CK backplanes were scarce.
To solve that problem he changed the wire wrap on the DD11-Bx backplane that was installed in the machine to the modified Unibus structure for the slots 2 and 3, rows A and B. He did this with a wire wrap hand tool. That is how he got the "DD11-CK".
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The front panel of the PDP-11/05 has a few more buttons, switches and lights than the average Personal
Computer, as you can see.
I guess this "personality" is what makes these old systems 'beautiful' when compared to a modern PC.
The console has 16 LEDs for display of an address or the data contained in an address. One LED indicates if the processor
The meaning of all these lights is explained a bit further.
From left to right there are 16 switches to set up an address or to load data. The up position represents a logical 1, and the down position corresponds to a logical 0. The ADDRESS/DATA switches are often referred to as the "Switch Register", SWR.
The following 3 buttons (momentary push down) for LOADing and EXAMining an address and to CONTinue the CPU, a switch to ENABLE/HALT the CPU, one button (momentary push down) to START the processor and one button (momentary push up) to DEPosit data into a memory location.
At the right hand side is the key switch to turn off / on the system and to lock-out the switches and buttons on the panel while the system runs.
Control over the system via the console
|KY11-J programmer's console indicators|
|16 LEDs||The 16 LEDs either represent
a 16-bit address the contents of a processor register or a memory location.
Note that the state of the ADDRESS/DATA LEDs is defined only when the RUN LED is not illuminated.
|RUN||The RUN LED, when lit, indicates that a program is being executed.|
|KY11-J programmer's console switches and buttons|
| 16 ADDRESS/DATA |
ADDRESS/DATA switches set a 16-bit address to be loaded or the 16-bit data to be stored in a processor register or a
These 16 switches are called the Switch Register, and can also be read from a program that is running.
|LOAD ADRS||Depressing the LOAD ADRS button down,
when the computer is halted, causes the contents of the Switch Register to be stored in a temporary register within
the computer. This data is also displayed in the ADDRESS/DATA lights for verification. The load address operation performs
the following functions.|
|EXAM||The EXAM button permits the display of the
contents of a selected address in the ADDRESS/DATA lights. Select the appropriate address in the Switch Register and
depress the LOAD ADRS button. The depress and release the EXAM button. The contents of the selected address is shown.
Several features are built into the examine function to aid in the programming of the computer.|
|CONT||The CONT button is used to continue a
program without altering the program counter, R7, or the machine state. To continue a halted program, depress and
release the CONT button. The program is resumed when the CONT button is released.|
The CONT button is used with the ENABLE/HALT switch to step through programs one instruction at a time. If the CONT button is actuated while the ENABLE/HALT switch is in the HALT position, a single instruction will be executed. Interrupts are serviced in single instruction mode. In single step mode, the address of the next instruction to be executed is displayed in the ADDRESS/DATA lights.
|ENABLE/HALT||Place the ENABLE/HALT switch in
the HALT position; the computer will halt at the end of the current instruction providing the key switch is not in
the PANEL LOCK position. All interrupts and traps will be excuted prior to halting.|
This switch may be used in conjuction with the CONT button to step through programs. With the ENABLE/HALT switch in the ENABLE position, programs may be executed, once started by actuating the START button, actuating the CONT button, and the auto-restart power-up sequence.
|START||To start a program fron the console do
the following steps.|
Take not of the following precautions when using the START button.
|DEP||The physical operation of the DEPOSIT button
requires it to be lifted for actuation. The DEP button allows the contents of the Switch Register to be deposited in
a Unibus address, which is typically specified by a previous load address operation. To deposit the "BRANCH SELF"
instruction (777 octal) in location 200 octal, first set the Switch Register to 000200, and then actuate the LOAD
ADRS button. Set the Switch Register to 000777 the lift and release the DEP button.|
Several additional features are built into the deposit function.
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As usual, slot #1 is at the right hand side when you stand in front of the computer. So, from right to left you see the following system units (SU) in my PDP-11/05.
> All the system units are connected with a M9202 module.
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