I recently bought a new router the asus RT-N56U, and it has four gigabit ethernet ports on it, but for some reason on my pc i only get 1 mbps on three of the ethernet ports and the one in the middle lower half goes past 100 mbps
The speed a Ethernet connection is a negotiated rate. If there is any noise or interference on the line, the speed is lowered until the 2 devices can communicate with an acceptable error rate. In your case, my guess is there is a bad solder joint inside your router causing communication issues with the 3 bad ports (surprising ... normally it's just 1 bad port). You should return this router and get a new one.
The speed a Ethernet connection is a negotiated rate. If there is any noise or interference on the line, the speed is lowered until the 2 devices can communicate with an acceptable error rate. In your case, my guess is there is a bad solder joint inside your router causing communication issues with the 3 bad ports (surprising ... normally it's just 1 bad port). You should return this router and get a new one.