device nfe is part of the GENERIC kernel in 7.0+. No need to compile a custom kernel. You can confirm this by running
kldload if_nfe which will return "already exists" errors, as it's already part of the kernel.
If it's still not being detected, then the
nfe(4) driver in 7.0 doesn't support it. You can try an update to 7.1-PRERELEASE to see if the version of the driver in there supports that chipset. The update might be supported by freebsd-update. If not, you'll have to do a buildworld cycle using
tag=RELENG_7 (there's no RELENG_7_1 tag as yet).
Do any errors appear in
dmesg output? How about if you boot with verbose logging enabled? Does the BIOS have options to change how the network chipset appears? On some nvidia boards, you can select between
pin-strap (the default) and
mii modes. The mii mode is more standard and better supported.