The image on the top is Andrew's board just with the data bus D7 signal (since it's all the way on the right of J5 and easy to get the probe on) without the sound board hooked up. Pretty typical each time I ran/stopped it. (this is in attract mode). There were no tiny voltage spikes unless I just had bad luck stopping the signal randomly.
The image on the bottom is the MPU200 board in question, with 2xNVrams on it. Again, typical results but I did go out of my way to capture tiny spikes in the signal which may or may not be relevant, because when I pulled those NVrams out and put in 2xpihillips 5101's I had laying around (I really had to dig for those because I tossed most of my 5101s into a couple different places, and these were the 1st ones I found - they turned out to be good so there's that.)
I verified that the game played the sound correctly with those 2x5101's - I forgot to save the waveform with the 5101's in there, but it looked the same as the 2xnvram, with some tiny spikes in there.
The sound being messed up is all sounds except for the background sound - not just the spinner sound. This issue might be related to the software difference though, as it's built on top of the big game raw OS but with the Meteor sound routine in the IRQ grafted in.
I'll have to look on the sb300 itself to see what signals to probe there... I see the 6840 enable is tied to the o2 signal.
I'll also have to look through my board stock to see what else I can toss in there and see if it works - I know I have a working mpu200 with the old forge site's 6116 nv replacement mod on it and I probably have several other stock mpu200's (especially since I plan on replacing all those with Andrew's mpu boards anyway) to play with. I'll try and find one that is the later revision so that I don't have to worry about swapping the components back and forth so much.
I think the goal I have in mind is just documenting what all the differences actually are, with testing the sounds to see if whatever revision works.... then I guess seeing if applying the difference to the early board fixes the sound or not.
The thing that's really bugging me is that it was working 100% before a couple weeks ago.
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