> 
>  > Hah! OK, Stick a floppy in your disk drive and boot! The kernels that hang
>  > at root on sd0 now boot!
> ...
> Nonetheless, the problem has recently "appeared" ... I.e. I used to be 
> able to boot without a floppy in the drive ... maybe I'll go try out that 
> hypothesis later on today (gotta go into work to test it out). 

Turns out we had a border-line polling loop in fdattach() that ran out of steam
too early. Since delay(n) used to take almost 2*n microseconds before returning,
the fdc was polled just long enough on some (but evidently, not all) machines.
Anyway, I changed fdattach() to wait up to 10 seconds for the chip when
probing for drives.

-pk