multiple timing errors in 10GBASER phy core on clock nets xv_xcvr_10gbaser_nr_inst|ch[0].sv_xcvr_10gbaser_native_inst|native_inst|inst_sv_pma|tx_pma.sv_tx_pma_inst|tx_pma_insts[0].sv_tx_pma_ch_inst|tx_pma_ch.tx_cgb|pclk[1]

Hi,

Fitter overconstraints are timing constraints that you adjust to overcome modeling inaccuracies, mis-correlation, or other deficiencies in logic optimization. You can overconstrain setup and hold paths in the Fitter to force more aggressive timing optimization of specific paths.

You may refer to https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/ug/ug-qpp-timing-analyzer.pdf

2.2.9. Using Fitter Overconstraints

Thanks.