It depends on the driver. most of the drivers for it was made for the intel mac (say what? PCI in an intel mac??)

Try the 10.3 drivers if it's there. I might have them so I could send those or put them up on my server. but that should get you started. Let me check my FTP server and send you the link. that should get it working (I have used a 8169 PCI Realtek card for a while in my machines, and I KNOW it works in OS X)