If it is really gigabit ethernet, can you find ethernet phy chip? Usually it's realtek one. DT, which I extracted from Android image, says TX6 has RMII interface which would suggest 100 Mbit ethernet.
It was sent to me as Gigabit, but now I carefully examined it , there 100Mbit.
By the way, you saved my TX6 from the trash where I wanted to send it (I only need Linux-enabled devices).