Calculate skew timing with Cyclone V and ksz9031

Hello,

i have additional questions.

we tested now more than 10 boards with our new device tree, and have the following result.

File embedded system => PC:

if we copy an file from our embedded system to the pc, we have no or less retransmission, < 5 retransmission per copy.

all 10 boards have the same result

File PC => embedded system:

8 boards:

if we copy an file from our embedded system to the pc, we have no or less retransmission, < 55 retransmission per copy.

2 boards:

have really a lot of > 400 ack retransmissions, and ack fast retransmissions.

Result:

the ack retransmission error is always from pc to our embedded system, which connection is bad.

Where can we start troubleshooting?