Communication with gpio(De2-70)

Hello,

I realize a communication between two kits DE2-70 by the gpio. Communication is 100MHz (Stream Avalon) with a flat cable. But there are too many problems, erroneous bits, ...

I was told it is certainly possible to increase the output current of ios but I do not know how we do this?

I was also talk of increasing fanin and fanout but I do not know how.

Can you explain the method to be followed to achieve this?

Or any other suggestions for improving the transmission?

Thank you.