DEC PDT-11/150 – Part 2.

In the last post I described the PDT-11/150 a little bit and the state of play. It was showing signs of life but not talking to me.

It turns out the cable wasn’t right. Switch to a new cable, fire up GtkTerm and we’re on the right lines.

What we have here is the ODT display. It doesn’t look much but it shows us that the machine is alive and conscious.

Main switch settings.

There is a five switch DIL pack on the top board that sets various options for the machine. The manual gives the following explanations:-

IT seems a little odd that the switch labelled “Auto Baud” should be set to off to turn Auto Baud on. Really? Ah well.

Mine are set as follows:-

  1. ON – Auto Baud is disabled. Baud rate is set to 9600.
  2. ON – Line clock is disabled.
  3. OFF – Enable the DRAM refresh.
  4. OFF – Disable the test mode.
  5. OFF – Disable manufacturer mode.

Setting the switches this way I can get to the prompt you see above.

I have tried getting into the test mode but it doesn’t seem to work on my machine. I wondered if the self test at power up is failing and dropping me into the ODT but the error light on the front goes out so I guess not.

I haven’t turned on the line clock as I don’t know yet if I need an interrupt handler for it. Clearly we need DRAM refresh and fixing the Baud rate at 9600 is just A Good Thing (TM).

Booting?

Now here’s a thing. I can’t find any information about how to get this thing to read a floppy. The manual describes setting the switches to get test mode. It says how to insert a floppy and how to handle them safely but nothing on how to boot the machine.

I’ve looked at both the technical manual and user guide (thanks to Bitsavers) but there is nothing.

A little test.

Although I can’t boot from floppy, I can fire in code using the terminal and things are starting to look brighter.

Here is an example from the ODT page on wikipedia.

This fires the letter ‘A’ at the console port as fast as it can and only stops when you press the reset switch.

Tada!

 

 

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