I builded a project(Gigabit Ethernet Interface) used cyclone IV ,it works well on 1000M bps 100Mbps 10Mbps;(TSE+KSZ9031)I change the project and now it can wok on cyclone V(5CGTFD9E5F35C7)(TSE+Marvell 88E1111),it can works well on 100Mbps, but in 1000Mbps mode ,on pc I can receive the ethernet packet sended by FPGA Ethernet Interface ,but I found error bytes. for example:part of send data: 00 1c 23 17 4a cb part of receive data 00 5c 33 77 4a 9b my idea to solve the problem 1：in 1000Mbps, I Set TSE into loop mode ,I can receive the packets which i sended. so i think the problem is the RGMII timing problem, but I changed SDC about the rgmII interfae ,but can't solve the problem? help me!! thanks !!