it's doing something very strange that is both worrying me and giving me some hope. it's only reading the empty drive if the failing one is not plugged in. i mean at a bios stage. i've reset the cmos and it's not helping.
so i'm going to start swapping cords around. i don't see why plugging in the failing hard drive should stop me from reading a functional one.
if it's a board problem, that's a bigger issue. but it might mean i can get the info off. which is what's important. i can replace a dead drive relatively easily. i can't replace some of what's on it without a great deal of effort.