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PDP-12 #435 at the University of Minnesota Duluth

ZachyCatGames said:
The PAL12 on our LINCtape spammed `IC ILIST` forever (seemingly, I don't have infinite time available, unfortunately...)
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Update: It does eventually finish, it just takes like 15 minutes to do so. Attached a log for 57236.pal, not gonna both repeating for the other pal sources unless requested.
 

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antiquekid3 said:
Do you want to try getting my implementation running?

github.com

GitHub - drovak/pdp8life: Conway's Game of Life for the PDP-8

Conway's Game of Life for the PDP-8. Contribute to drovak/pdp8life development by creating an account on GitHub.
github.com github.com
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That sounds like fun, but would your video code work on the PDP-12's VR12? You probably know this, but VR12 uses LINC instructions for display, etc. (Perhaps you were suggesting that we modify your code to use LINC instructions to add PDP-12 support?) Regardless, it sounds like a fun thing to add to our todo list.
 
pahp said:
That sounds like fun, but would your video code work on the PDP-12's VR12? You probably know this, but VR12 uses LINC instructions for display, etc. (Perhaps you were suggesting that we modify your code to use LINC instructions to add PDP-12 support?) Regardless, it sounds like a fun thing to add to our todo list.
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Ah, I see you have text-mode output!
 
We had it running on Vince's PDP-12 last year. I think we just hacked the display routine in an afternoon to get it working properly.

PXL_20230825_181022606.jpg

If someone wants to add proper support, I'll happily pull those changes in.
 
pahp said:
What is "mark parity" in this context?
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When I copy things to and from media images, I find that I have to clear the 0200 bit of each byte to get them to display correctly on my modern machines. That, in turn, creates a problem of needing to set the 0200 bit of each byte when I move them back into the PDP-8 world.

I've had the problem a few times where I failed to do that, and the PDP-8 gave weird results. These are what the 8tools "2asc" and "2mark" are for.
 
vrs42 said:
When I copy things to and from media images, I find that I have to clear the 0200 bit of each byte to get them to display correctly on my modern machines. That, in turn, creates a problem of needing to set the 0200 bit of each byte when I move them back into the PDP-8 world.

I've had the problem a few times where I failed to do that, and the PDP-8 gave weird results. These are what the 8tools "2asc" and "2mark" are for.
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Thanks -- we can look into that.
 
vrs42 said:
When I copy things to and from media images, I find that I have to clear the 0200 bit of each byte to get them to display correctly on my modern machines. That, in turn, creates a problem of needing to set the 0200 bit of each byte when I move them back into the PDP-8 world.

I've had the problem a few times where I failed to do that, and the PDP-8 gave weird results. These are what the 8tools "2asc" and "2mark" are for.
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Running `2mark` on `16383.pal` doesn't appear to have made a difference. Using `TYPE`/`FOTP` to print out the contents of both pre and post `2mark` copies of `16383.pal` also gives identical results. Opening the post-`mark2` copy in a text editor on my PC does show a bunch of garbage though. Do the `os8xplode`/`os8implode`/`mkdsk` scripts already take care of this?
 
Hi all, the semester has been super busy so I haven't posted much, but @ZachyCatGames has been busy with the PDP-12. He got it to run Whetstone in Fortran (no FPP of course), and is implementing Dhrystone in assembly. (It's basically done but needs timing code and some double-checking.) He's been learning TECO and using the on-screen display of text as an editing aid -- pretty revolutionary for 1972.

@antiquekid3 sent us a couple replacement fans as one of our Boxer fans cooling the flip chips has been making a terrible grindy sound. We got new leads soldered onto the fan and even found some spare spade connectors laying around so we didn't have to damage the original fan. At first we were confused about the lack of threads in the fan holes, but upon visiting my local hardware for nuts and bolts, I recognized the screws we removed from the old fan as self-tapping screws. So I bought some new screws and we got the new fan installed. (I've got to say, screwing in self-tapping screws for the first time feels extremely wrong. But it worked great.)

PDP-12 #435 once again sounds like a beautiful dream soaked in white noise! Thank you very much, @antiquekid3 !
 

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antiquekid3 said:
Great! Are the fans all blowing in the same direction?
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That is an interesting question!

I would have mounted them to be visually similar (i.e., logos pointing out). However, @ZachyCatGames noticed that the original fan and the new fan both have arrows indicating (presumably) airflow direction. We verified that wind blows in the direction indicated on the new fan, and we mounted the new one as shown in the image so that its arrow points the same direction as the old fan (towards the flip chips). However, we did not confirm that the fans are all blowing in the same direction. We will do so and report back.
 
pahp said:
That is an interesting question!

I would have mounted them to be visually similar (i.e., logos pointing out). However, @ZachyCatGames noticed that the original fan and the new fan both have arrows indicating (presumably) airflow direction. We verified that wind blows in the direction indicated on the new fan, and we mounted the new one as shown in the image so that its arrow points the same direction as the old fan (towards the flip chips). However, we did not confirm that the fans are all blowing in the same direction. We will do so and report back.
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We confirmed that all fans seem to be blowing in the same direction -- towards the flip chips.
 
pahp said:
(I've got to say, screwing in self-tapping screws for the first time feels extremely wrong. But it worked great.)
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A bit of "lost knowledge" about self-tapping screws: When inserting the screw back into a hole that previously had a self-tapping screw in it, do NOT simply start tightening - you'll cut new threads and weaken the plastic, until eventually the hole is stripped out. Instead, turn the screwdriver counter-clockwise slowly. You should feel (and maybe hear) an obvious "click" when the screw drops into the previously-tapped threads. Now switch to tightening and the screw should go in with very little force required, since it's using the previously-tapped threads.

The same thing can be helpful when trying to put a nut on a machine screw "blind" - it will similarly "click" when the screw's threads are lined up with the nut.
 
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