PDP-11 diagnostics - search the database

Parent Category: How-to's Category: Using PDP-11 diagnostics Written by Administrator

All known files and documents are accessible over the diagnostic database. Here's an example how to find the right diagnostics for a specific hardware.

Case study: a sick PDP-11/34 processor.

Recently I acquired a set of CPU boards (M8265 and M8266) for a PDP-11/34a. Soon I suspected they had a problem, but power-on selftest and booting RT-11 was OK. So to find the error I needed to run all of the processor diagnostics.

pdp1134 under test


1. Which devices are left over to run the diagnostics?

Before searching in the database, you must decide how you want the diagnostics to run. See here about possible options. Depending on your hardware, you may only use old paper-tape images, XXDP boot media or single *.BIN or *.BIC files.

2. How do they call my piece of hardware?

A PDP-11 system consists of several hardware components, which can be tested independently.

A hardware (or software) component is always called "Device".  To find out what diagnostics for a device are available, you search at first the database by the "Device Index".

Using your Browser's Search function is a good idea!

diag database device index

The list is big, and device names do not follow any standards!

Luckily the "11/34" link is easy to find.


3. Search the list of test modules

A test "Module" is just another word for "diagnostic program". But also manuals may have module numbers assigned by DEC.

diag database module list

Test modules appear at various places on the web under different URL. All those variants are listed here ... expanding the list beyond need.

Test modules also come in many versions, as they developed over time.
Older diagnostics typical consists of many short individual tests, since they were distributed on paper tape stripes.
Newer diagnostics are saved on tape or disk and run under the XXDP system, were length is not an issue.
A late XXDP diagnostics may combine many earlierer ones into one program.

For every module a short description line is given, but you can click onto the module link and check for more info in manual pages or program listings.

Back to our PDP-11/34: For a plain 11/34 without floating point and cache, these tests are found:

  • FKAA - basic instruction test ("is it a PDP-11?")
  • FKAB - trap test ("can it interrupt?")
  • FKAC - extended instruction set test (EIS instructions, like MUL and DIV)
  • FKTH - memory management (FKTA to FKTG are older tests)

4 Download the program files and assembler listings

Use the hotlink for each test module and explore the available downloads.
You basically need two files:

  1. a runnable image (XXDP and/or papertape)
    For XXDP, the program may come from one of three possible disk images: XXDP+, XXDP2.2 and XXDP2.5.
    You can download the individual *BIN or *.BIC program files, but of course you will boot from the corresponding XXDP disk or tape, if possible.
  2. the assembler listing with complete MACRO-11 program code and running instructions.
    The listing is essential if a diagnostic fails: most programs only print the error location in the test program!
    And the program documentation is excellent.
    Often there are additional files with manual pages, but the information there is always a subset of the assembly listings.

diag database fkac resource files


My 11/34 has an RL02 disk drive attached. FKTA, FKAB, FKAC and FKTH are all contained on the XXDP 2.5 disk, so executing them is easy.