While ibert test shows an open eye for FMC MGT 0..3 even for 12.5Gbps, the performance of MGT4 and MGT5 is much worse:
MGT4, 8Gbps, PRBS 15-bit:
MGT5, 8Gbps, PRBS 15-bit:
MGT4, 10Gbps, PRBS 15-bit:
MGT5, 10Gbps, PRBS 15-bit: