• Please review our updated Terms and Rules here

What did I do to my PDP-8 today.

PXL_20230823_174956157.jpgPXL_20230823_174934338.jpgPXL_20230823_174946292.jpgPXL_20230823_082511818.jpg

More pictures. We brought up Doug's famed Console Serial Disk on the 12, and lo and behold, it booted and ran ADVENT just fine. Amazing! This was streaming from the CSD server at 115.2k baud. Not bad at all.

We ran DHKMAD.DG and found some odd behavior with printing. Ran it on the 8/E with CSD and it ran just fine. Yep, turns out it's an 8/E-only diagnostic and uses BSW. Dang it... Now we need to find a proper extended memory test program for the 8/I or 12.

Saw one case, just once, where the 12 locked up presumably from not receiving a MEMDONE signal... Need to do more stress tests to ensure the memory is stable.
 
That is beyond cool but I'm really jealous too.

Hanukkah Claus can you please bring me a PDP-12 to keep my lonely PDP-8/E companyo_O?
 
I'd be happy with an 8e. The 12 is kinda large. But if one showed up I'd be happy.
 
I finally have my 8/E up and running with the RX02 and with serial disk. Next is to get it running with the EAE and then the RK05.
 
I wish I had kept my 32k dual RK05 8e system. But alas I did not. It was a really nice single rack system.
 
Ran the D1EC memory test for quite a while and got through all of the fields. No issues to report. Sweet! Checked the various memory timing signals and they look nice and clean as well. I will have to study the design more, but I think there's a possibility of the flip-flops coming up in a state that prevents the next memory cycle from ever completing, hence why we powered up the system and couldn't get it to work, yet powering it down and back up fixed it.

PXL_20230824_044554886.jpg

We also tried the VR14, and it too shows signs of life. We hand toggled in KALEID to get the VR14 lit up, and it responded well to two of the analog inputs. Very neat! Seems as though there are some issues with the horizontal DAC, and the yoke seems rotated. It also is showing a circular shadow on the edges, so it's nowhere close to filling the screen. Definitely needs work, but this obviously is a very functional CPU from what we can tell so far.

PXL_20230824_060042921.jpg
 
Thanks Kyle, for keeping folks up to date with our shenanigans! (Not to mention your help with the actual shenanigans.)
 
antiquekid3 said:
The text plot is from the VC8TST program, which is just exercising drawing text on the screen and not much else. I am sure it's up on Vince's site somewhere in the depths of the repository.
Click to expand...

I did not find VC8TST on Vince's site, but would love to have a copy and if it exists the source.

antiquekid3 said:
The VC8E clone is Vince's design using our favorite ATF1508 CPLD as the main brains, but the current Verilog description is taken directly (though tweaked slightly) from the schematic translation tool Vince wrote in Perl.
Click to expand...

Very cool!!!
 
PXL_20230824_184705381.jpg

We tracked down a bad half of a 7474 (shocking, I know) on one of the the A615 DAC cards, hence why we saw stripes on the screen. After replacing it, we have a nearly proper looking output, other than some previously mentioned issues with the VR14 and perhaps some other adjustments.
 
PXL_20230825_011419305.jpgPXL_20230825_011418153.jpgPXL_20230825_011339759.jpgPXL_20230825_010237617.jpgPXL_20230825_003602096.jpg

More VR12 screenshots. We found the transistor for the MSB of one DAC was defective. After replacing it, we now have an essentially square picture. However, it still has what seems to be a yoke problem. I'm assuming it simply fell backwards on the neck of the CRT and rotated some. Need to tackle that next, unless we get distracted with LINCtape drives!
 
PXL_20230825_054710004.jpgPXL_20230825_054720573.jpgPXL_20230825_054730832.jpgPXL_20230825_054741191.jpg

Well, our suspicions were right—the yoke slid back on the neck and rotated out of position a bit. Sliding it back down and aligning it to the best of our ability within a few degrees, the VR14 is looking rather marvelous. Vince has himself a nice looking display! I'm modifying my Game of Life implementation to run on the 12, so maybe that will be ready to run soon.
 
PXL_20230825_055348659.jpg
PXL_20230825_055355932.jpg
PXL_20230825_055403423.jpg
PXL_20230825_055423803.jpg
PXL_20230825_055441345.jpg
PXL_20230825_055454678.jpg

And some shots of KALEID. For what it's worth, the manuals specify that the horizontal pitch is larger than the vertical pitch, or in other words, the aspect ratio should be rectangular and fill the screen. However, I feel like the square aspect ratio looks better. I guess Vince can decide what he wants to use—right now, it's square, but a single pot on the horizontal deflection amp board in the VR14 can change that.

I suspect we'll look at the broken auto start function and why the START 20 switch is flaky next. Or, maybe see if we can get one working TU55 from three broken ones...
 
You must log in or register to reply here.
Back
Top