Q: Building PiDP-8 software on RPi 400

[Ken Hansen]

Hello,
I wanted to play with the PiDP-8 software, pidp8i, on an RPi 400 (RPi 4 w/4 Gig RAM in keyboard case), but I ran into an issue.

I installed the latest, 64-bit Trixie w/ desktop OS and worked through Recipe 1 on the PiDP-8 Quick Install Instructions, but when I finished, after I rebooted the 'pidp8i' command didn't get me into the simulator, I got the following error message:

Either the simulator isn't running, or it isn't running under a screen session owned by pi. Did you start the simulator via systemd?

User "pi" is the only user on the system.

Any ideas what I'm missing?

Is the trixie OS not supported? Is there some step I likely missed?

I started this project when I saw Microcenter was having an in-store sale on the RPi 400, the system was only $40, a tremendous discount over the current price of a regular 4 Gig RPi 4...

Thanks in advance,

Ken

[Jeff Jetton]

Sounds like the simulator isn't being automatically started on boot. Using "pidp8" by itself just attaches you to the currently-running instance. If there isn't one, try using "pidp8 start".

See: https://tangentsoft.com/pidp8i/doc/trunk/README.md#using

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[Ken Hansen]

So, after a few hours sleep I came back to this and read Mike and Jeff's suggestions, as well as reviewing the Quick Install page again, and I got it running.

What I did was I ran the special steps that loaded a different GPIO library just for RPi 4 (and presumably RPi 400) in Recipe 3, and then executed the last command:

tools/mmake && sudo make install

Then I rebooted the RPi and that did the trick, pidp8i got me right into the running pdp-8 emulator.

I'll start playing with it soon, but everything seems right after some basic poking around.

Thanks Mike & Jeff,

Ken

On May 9, 2026, at 05:29, Mike Katz <justme...@gmail.com> wrote:



Try:

>pidp8i start

>pidp8i

Though the installation should setup the software to autu run on boot.

I tested this build on bookworm & trixie on RPI4 and RPI5.

If that doesn't start it, try using my install script to reinstall.

https://drive.google.com/file/d/1IjbIIns5Kr1s4Y6dl4ZSS2-_zqFZhOoD/view?usp=sharing

Good luck.

    Mike