In compiling the list of compatible gigabit adapters I came across
something that is confusing to me and was hoping someone more
knowledgeable could explain.

Both
em -- Intel(R) PRO/1000 Gigabit Ethernet adapter driver
gx -- Intel(R) Pro/1000 Gigabit Ethernet adapter driver

From the man pages, both of these support 82542 & 82543
How does the kernel know which driver to use, or does it really make a
difference ?
Or is one driver a more recent version than the other ?

hmmm...

- Don