Somewhat related, I had an older Asus core 2 board, that would accept 16gb of ram, but would only work on 64 bit OS's. However, even with a 64 bit OS, the onboard NIC would fail to work. So I added a NIC to the PCI bus, and it also wouldn't work. I could only get a USB dongle NIC to work. Really weird, and never solved why it was doing this.