I just figured it out from first principals of how RAM works and the pinouts of memory chips and SIMMs. There probably is a good article on it somewhere, but I haven't found it.
I think I wrote a fair amount of explanation in a posting I did here, where I discussed my testing of various Mac logic boards with 32MB, 64MB and 128 MB SIMMs. That might have been on the old board before the crash, I'm not sure any more. And I've discussed the topic multiple times, so finding a posting by me on that topic isn't necessarily the one with all the careful explanation in it.
It was before Braun started doing his magic and increasing the RAM limits on the Q650.