Many thanks, and though I don't understand all of what was said (which is a common occurrence for me), I get the general idea well enough. So, before I chuck the RAM in the eBay bin: Are there Quadra-era Macs or early PPCs that 72-pin 64MB EDO chips would work in?

I'd rather not go tearing down a Quadra 800, for instance, if the wee beasties just aren't going to be recognized as 64MB chips in it. On the other hand, if they would work in a Q800, A/UX 3.1 running on a machine with 256MB RAM would make the tear-down well worth the trouble.