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Great job! Huge congrats!!! Glad it's finally fixed! It was a great board to certify - run it with a Thunder ROM in it and ditch that PDQ+ one. :) Don't second-guess yourself too much. It was a very educational process, as you say! And, you did a great job that also benefits others. The main...

Great job on the detailed debugging! Lots of information! Some suggestions/ideas: 1. You can try writing all $a or $5 as the data (max transitions) - that might help when scoping. Alternate the pattern on each successive write. (non-random worst-case data pattern) 2. It could be noise -- where...

re: interrupt disable -- good. It shouldn't matter, as above, but just ruling it out. So, you know you are dealing with an issue that is explicitly affecting the blue component of the data path without any outside interference. Parenthetically, in the case of SuperMac graphics acceleration...

Macs have soft cursors that are updated on a vbl task (during blanking/interrupt time). They do not replace what is on screen, but rather do a copy OR after saving the cursor region. Cursor functionality is part of the OS and is not specifically linked/associated with video cards, except to the...

I tried a bunch of different code-based HiliteMode operations (ovals, rectangles, images, patterns, etc.) on my PDQ+ with a Thunder ROM in it. No weirdness that I could see, but still have to do text. Anyway, a hardware problem seems very possible/likely. My ROM is: Thunder/24 1.6.01, Quadra...

Interesting trace. Based on the code you are showing, it looks like it could be accelerator code to me. There are 3 possible clues: 1. D5/D6 have what appear to be Thunder/PDQ+ super-slot addresses for a card in Slot E. Is the card in Slot $E? For QD (or accelerator) operations, there is...

For 1992 and earlier (up to Thunder), SuperMac boards had no extra row space, as you calculated above. However, after 1992, there were multiple considerations relating to PowerPC (as suggested above - 1994ish?) and also, possibly, the onboard daughtercard accelerators (GX). Either of those...

Great job, Bolle!

Something on the board. Who knows? If it works, count your blessings and forget about it. 😜

OK. If the values were low, then the parts may have had weak shorts (debris, gunk, whatever). They are probably 5% tolerance parts. But, if so, then you fixed them. Check them again on the board to see if they read correctly now. The data might confirm this issue.

Great job - blown resistor! It's alive!! 🧟‍♂️ - "Fraaaaaames..." Another vintage board back from the dead! :love: Big Congratulations! n.b. The other 3 resistors with weird values could have had non-obvious shorts that you fixed by removing them (if the values were low), cleaning the pads...

I really hope it works out!

I thought there was a respin at some point, but maybe not. Maybe just the 8*24 fix and PAL->GAL cost reduction (that would have also required different/recompiled device files). I will find my boards and check them for the rework.

It will be exciting to see what happens this week on...Bolle-ing for Diodes! :D Regarding my earlier recollection about NS PALs vs. Lattice GALs, the fact that the parts are sanded does not necessarily mean that they were the NS PALs, but it's possible. I wouldn't beat yourself up too much...

Yes - they are sanded on the original (probably earlier) board. But, now that I think of it, there is no guarantee that the original part is the same vendor as the newer-looking board with Lattice parts. I think the original design included National Semi (possibly PALs) that were then switched...

Yes - damage to the part is a possible outcome. Sorry to hear that happened. Maybe you should send the good one and only try to read that specific part. Then, if you can read it, program a new device, replace it into the old board and see if it works again. If so, then proceed using the old...

OK - sounds good. The full waveform for U19 should be helpful. Testing every resistor value is not necessarily the same as testing the resistor connections to the board. The resistors could be OK, but there could be a dry/bad solder joint. You don't have to remove them from the board. For...

Send the bad one! :D But, if it worked, that would be pretty awesome! :love:

I just woke up and had another thought. There might not be anything wrong. The problem might be a missing or broken resistor. You said that you thought the board took an impact, and in that kind of scenario, it's possible to lose or fracture ceramic discretes -- especially in the case of weak...

I don't think the reading trick is guaranteed -- but maybe Bolle could comment. .I think there's also a chance you might damage the part, whether or not it worked.