I have a couple of older Dell desktops with this problem in the e1000e chip on the motherboard. tso off is all that is needed to avoid the "Hardware Unit Hang" crash. Install ethtool and add a line to /etc/rc.local: ethtool -K eth0 tso off
Realtek chips avoid bugs in their optimization hardware by-- not having any optimization hardware. The RTL8111 is little more than a bit pump. They will use a lot more CPU per packet than Intel.