Interessant.

So the same card in the IIsi works, while the IIci does not.
The NuvoLink card works in the IIci in the same slot that the
Asante does not work in.  The Asante Troubleshooter fails to
read the expected byte from 0xfeed0000.

0xfeed0000 doesn't look much like anything.

Can you get a MacsBug dump of 0xfeed0000?  Can you try writing a value
to 0xfeed0000 and reading it back?  Do you have a cache card in the
IIci?  If so, can you try the same tests with that disabled?

-allen