After more investigation:
It seems the last 5 voltage domains look more functional, and those are the ones powered off what appear to be separate regulators.
Looks like i gotta rip off some heatsinks to investigate further.
i pulled off all the heatsinks
that was some HOT fun. now i can understand the design & layout much better. i also pulled off the first 2 ASICs, that I thought were maybe shorting something to ground, but that did not help.
the buck/boost still makes noise. more investigation.
Just out of curiosity, how many versions of the S9 hashboard are there?
Edit Update: Found one of the 1V8 regulators putting out 1.5V and pulled the ASIC near it, and that seemed to make everything happier. No more noise from the switching supply. Now I'm debating if i want to put new BM1387 on there or just chalk up the board for more experimentation.