PDP-11

PDP-11/40 Running Diagnostics

Ashlin Inwood

• 2 min read
PDP-11/40 Running Diagnostics

So you have a PDP-11/40 and are now at the stage where you need to start running diagnostics? Well, I have the guide for you!

Required Equipment

  • PDP-11/40
    • Memory
    • DL11 (Can be emulated)
  • Unibone
  • Terminal or Terminal Emulator

Background Information

The primary diagnostics tool for PDP-11s is XXDP. XXDP is effectively a little operating system with a collection of pre-compiled diagnostic tests distributed on discs. XXDP has a lot of capabilities that we don't care about. Our only use for it is to load pre-compiled diagnostic tests into memory so we can run them.

Diagnostics are named using a schema; you can read more about that here. For our purposes, we don't need to know what the name means, as we can just search for diagnostics by file name.

Finding Diagnostics to Run

The most important resource is the PDP-11 Diagnostic Database, which is where you will find all the information you need to find diagnostics.

Example Diagnostic

To start, think of the piece of hardware you want to test, for example, the PDD-11/40 CPU. Start by going to Device Index them to 11/40. You can then scroll down the list looking for something applicable.

"BQEA - 11/35/40 CPU DIAGNOSTIC" stood out to me as something broadly applicable to my needs. Next, you need to track down the "listing", which is a document that contains the manual for the diagnostics and its source code listing.

If we click on the link for the BQEA, we will be taken to a page that lists all the other files associated with BQEA. In this case, it lists the pre-compiled diagnostic test and several revisions of the BQEA manual/listing. Now you have identified a diagnostic test to run, it's just a matter of trying to run it.

Running Diagnostics

I will assume that you have a functioning PDP-11/40 and unibone with some basic understanding of how to operate them.

Loading XXDP

  1. Power on the PDP-11/40
  2. Tonggle in at 00010 777 and run it
  3. Log into the Unibone and run <PDP-11 program name>
  4. Start XXDP at <Address>

Loading a Diagnostic

Each diagnostic may have unique loading and running instructions; refer to the relevant manual for detailed instructions.

In the case of BQEA the steps are as follows:

  1. Load BQEA into memory (L BQEAC1)
  2. Run BQEA from the console (Start 100), ensure all switches are in the off state
  3. Enjoy!

Diagnosing a failed Diagnostic

Refer to the diagnostic's manual for instructions.