The bandwidth specs on your router's spec sheet are in
Megabits Per Second. One
byte contains eight
bits. To calculate the number of
Megabytes Per Second, the unit of measure you are reporting, simply divide the
Megabits Per Second spec by
Your router only has
100Mbps is roughly
11MB/s of throughput (what you are getting) is very normal;
12.5MB/s cannot be reached due to overhead and other factors.
To get around this without purchasing a new router, you simply need a gigabit switch (~
125Mb/s theoretical bandwidth). Plug the switch into one of the router's
LAN ports and then connect your devices into the switch instead of the router.
Example of a gigabit switch: http://www.newegg.com/Product/Product.aspx?Item=33-122-140&IsVirtualParent=1
Note that Gigabit switches are also commonly labled as
10/100/1000 switches and/or