how to add a new OS?

[Michael Graffam]

Recently I stumbled on a disk image of Ultrix 3.1 for the PDP-11. Works great in a standalone simh environment on my PC, but I'd like to run this on my PiDP simh environment. 

How can I wedge it in there? 

[steve...@gmail.com]

Michael,

It may not be difficult, except for a possible issue (below):

1) Choose a name for your new system, but the name has to be a legal folder name. I'll say "ultrix3d1" for this example

2) Create a new folder in "/opt/pidp11/systems" called "ultrix3d1"

3) Copy all of the system  files you need, e.g., the disk image and any others if needed, into that new folder

4) Create an appropriate "boot.ini" file in that new folder that contains the SIMH initialization script to boot your instance of Ultrix 3.1

     You can look at the boot.ini scripts in the other folders under "/opt/pidp11/systems" as examples

5) Edit the file "selections" in "/opt/pidp11/systems". Choose a unique octal pattern for the left column, say 0120 as an example, and put

    the folder name "ultrix3d1" in the corresponding right column. It may or may not be important for the octal patterns to be in sequential order

6) Save the "selections" file

7) Reboot the PiDP-11 with your unique octal pattern, e.g. 0120, in the switch register, your Ultrix 3.1 system should now be running

The possible issue is that your Ultrix 3.1 disk image needs to be able to run on an 11/70 CPU. The line "set cpu 11/70" in "boot.ini" sets that. If you set to any other cpu then SIMH will run but the blinkenlights on the PiDP-11/70 front panel may not work. The underlying issue is that the connection between SIMH and the PiDP-11/70 panel uses bus signal names that vary by CPU type. When the bus signal names don't match between the selected SIMH cpu type and the PiDP-11/70 then that connection fails and the front panel won't work. SIMH will run, but the blinkenlights won't appear.

Cheers,

-- steve

[Michael Graffam]

Thanks Steve, 

I'll give this a whirl. I just went ahead and rebuilt an Ultrix image using the 11/70 specs. So far so good, and I have it loaded up with all the layered software available in the tape image I have.  Just have to get it wedged onto the PiPDP setup and do a little knocking around to figure out how to configure the virtual serial ports in Ultrix to come up with getty's automatically (I configured a DZ device on port 4000). 

Once I get it all together, if folks are interested, I'll post a DL location for a tarball of the whole thing to make it easy for people. It requires some goofing around to get a partition setup big enough to fit all the layered software. The installer just plows ahead and makes an 8M /usr partition, which isn't big enough. All the options takes 12M. 

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[Michael Graffam]

On Thu, Jul 15, 2021 at 4:45 PM Clem Cole <cl...@ccc.com> wrote:

Wed did not have the big disks when we did the Ultrix work on the 11's - Fred Cantor was amazing at what he smashed into that system ;-)

FWIW:  It would be helpful to put the URL's of where you sourced the files.  IIRC 3 was the last PDP-11 release.   4.0 was supposed to be the last Vax release but somehow we did a few after that too since Alpha was so late.

Simh-usable tape image of Ultrix-11 3.1 is here: https://pdp-11.org.ru/files.pl?lang=en

I set the emulator up with a big honking rd54; have plenty of space free, and I'm going to include the source code for Ultrix 3.1 available here: https://www.tuhs.org/Archive/Distributions/DEC/Ultrix-3.1-src/

 

Thanks,

Clem Cole

Lead for Ultrix 4.4 and 4.5 years ago ;-)

ᐧ

Rock on! I'm running an Ultrix 4.5 install on simh/vax as a way to probe the Thinking Machines Connection Machine materials. I have a large ARM cluster running Common Lisp, and I've been slowly hacking the *Lisp simulator to run distributed across my cluster. The front-end (DEC / Sun) materials aren't directly useful, since no emulator handles the CM VME interface, but they have both been helpful as points of reference to understand how things were supposed to work. 

[steve...@gmail.com]

I'm happy to help, Michael. And thanks for reading my mind. I would definitely be interested in getting a tarball of a workable Ultrix image for the 11/70.

[Michael Graffam]

I'm happy to share the tarball, if/when I get it prepped.  Unfortunately, that is proving to be tricky. 

Following your procedure doesn't work. 

/opt/pidp11/systems/selections gets re-created at system reboot, it seems. 

I have the Ultrix disk image all prepared and ready to go.. just trying to wedge it into the PiDP11 way of doing things. Hopefully I'll get a little time this weekend to really dig in, else it may be a few weeks because things are going to blow up at work soon and I'm unlikely to have much free-time. 

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[steve...@gmail.com]

"/opt/pidp11/systems/selections gets re-created at system reboot, it seems."

That is very strange behavior. I've never encountered it. I've added at least 3 new operating systems (RT-11 without the VT, PDP-11 Paper Tape Basic, and the Nankervis collection) following the procedure I described.

When you say the file is re-created at system reboot, do you mean:

*) When you are already in SIMH and you boot from one PDP-11 OS to another?

*) When you first "boot up" (i.e., start) SIMH for any PDP-11 OS configuration?

*) When you first boot up the Pi at power on?

The file should not get recreated in any of those cases, but knowing which is the case should help you narrow down on the cause. 

[Michael Graffam]

Rebooting the Pi. 

The selections file reverts to the 'stock' one. For that matter, the directory containing Ultrix disappears too!

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[Neal G.]

One possibility is that the SD card has become damaged. I have a card that exhibits that behavior. The Raspbian image on it boots and works perfectly, until I power down. When the system is powered back up; I find that all changes are gone and the filesystem has returned to what it was, on a particlar day in 2019.

There are some discussions in other threads regarding SD card problems that might be worth reading.

The solution for me was to replace the SD card.

- Neal G.