Newbie issue accessing OS/8

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Tom Coate

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Jan 2, 2022, 6:03:14 PM1/2/22
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Hello group! 

New member here. The PDP-8 was the first "real" computer I had extensive experience with, so was excited to discover these kits. I just got mine built over the holiday break, but have run into one thing I can't figure out. When I run the command pidp8i to access  OS/8 I see:

PiDP-8/I pkg:vUNKNOWN [pi3b] [ils] [stdpcb] [gpio] [rt]
PDP-8 simulator V4.0-0 Current        git commit id: 2f66e74c
Loading OS/8 from the RK05 cartridge disk...


But then the terminal hangs and is not responsive. I can use ^E to get back into SIMH, but nothing outside of that. Background:
  • Before building the kit, I'd loaded all the software on my Raspbery Pi 3 and confirmed that I could get into OS/8.
  • I built the kit, stopping to use the test program to verify that all the lights and switches worked correctly (including finding and fixing the one LED I'd put in backward).
  • After completing the build and firing things up, the system appears to boot and is running. I can use the front panel switches to halt the system, toggle in a simple program through the front panel, and have it execute successfully.
  • Booting into other configurations (TSS/8, ETOPS, OS/8 on DECtape) seem to all work, but OS/8 on Disk (switches 000 or 111) hangs as described above.
I'm suspecting I'm missing something that should be obvious, but would appreciate any insight.


Rick Murphy

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Jan 2, 2022, 6:21:28 PM1/2/22
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Tom,
Sounds like your "OS/8" disk is not bootable.
    -Rick


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Rick Murphy, D. Sc., CISSP-ISSAP, K1MU/4, Annandale VA USA

Steve Tockey

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Jan 2, 2022, 7:39:13 PM1/2/22
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Tom,
I agree with Rick. The most likely suspect seems to be a corrupted RK05 image. But not to worry. Do you have any important files on that OS/8 SYS: / DSK: RK05 disk image? If so, you'll want to set that image aside first. Assuming you know your way around Raspbian OS

1) Go to the directory:

/opt/pidp8i/share/media/os8

2) Rename the file

v3d.rk05

to something else, like

OLDv3d.rk05

If there's nothing important on that disk image, you can skip steps 1) and 2).

3) Go to the directory:

/home/pi/src/pidp8i/trunk/bin

4) Copy the file:

v3d.rk05

into the directory:

/opt/pidp8i/share/media/os8

That will reset you back to the original OS/8 SYS: / DSK: RK05 image that was first installed with the PiDP-8/I software.


The other thing to pay attention to is what SIMH tells you when you do the CTRL/E after it hangs:

Simulation stopped, PC: faaaa (iiiii)
sim>

What are faaaa and iiiii? faaaa is the memory address and iiiii is SIMH telling you (one of) the instruction(s) that it's hanging up on. It's possible to use that to figure out where in the boot process it's  hanging up (to some extent, anyway).


Good luck,

-- steve


Tom Coate

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Jan 2, 2022, 8:01:48 PM1/2/22
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Thanks, Steve & Rick, 

It seems like it must have been a corrupt rk05 file. I replaced it and it's up and running.  (And fortunately, nothing lost, as I'd not saved anything of consequence there.)

I really appreciate the help! Looking forward to settling in to play with this and journeying back down memory lane.

- Tom

Rick Murphy

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Jan 2, 2022, 9:29:25 PM1/2/22
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Steve,
Thanks for the info - I wasn't aware that there were pristine images there for recovery.
    -Rick

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Enrique Haro

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Jul 12, 2022, 12:02:17 AM7/12/22
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Good to know...... : )
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