freebsd dhcpcd failed

[gansteed]

Hello:
    I'm new to FreeBSD, I've install FreeBSD 10.2 on my PC, everything
works well except the network card, during the installation, it seems that
FreeBSD can recognize the network card, it says, "do you want to configure
dhcpcd for the ...blablabla `em0`?"  so I choose "yes", but I got lots of
"watchdog timeout error", I've searched for it, wiki says "To resolve
watchdog timeout errors, first check the network cable. Many cards require
a PCI slot which supports bus mastering. On some old motherboards, only one
PCI slot allows it, usually slot 0. Check the NIC and the motherboard
documentation to determine if that may be the problem." I don;'t know how
to check it, but it works well in Windows7 and ArchLinux. Is it possible to
fix the problem? I need your help.

    gansteed
    08/24/2015.