A FastEthernet port can theoretically do 100Mbps (Mega bits per second) which translates to 100/8 = 12.5MBps (Mega Bytes per second). Usually it's a 35% to 50% utilization with all the overhead. So that 12.5MBps goes down to about 5MBps. So you're getting the normal rate, I get the same too.
Try switching all ports to Full Duplex, it should show some deference.