I have the following problem. I bought two TP-LINK TG-3269 gigabit cards, placed them in two computers and connected them directly. On my Ubuntu system I used iperf tool and measured only 95 Mbit/s. It wont go any faster, I tried many times with different settings.
What is the problem? The indicator lamp shows 1000 Mbit/s.
1. check the cable. It needs to be a cat5 with all 8 wires working. Basic cable testers are very cheap by the way. A crossover or switch is not needed for gigabit.
2. you can set the speed manually somewhere in the driver, but i'm not an expert for linux. Research yourself.