Whatever way xvidtune -show gathers modelines does not seem reliable as I am
unable to reproduce the 586.00 line on AMDgpu, although it seemed so initially.

Testing old fglrx releases I found that 144hz does not work with 14.50.2.
The next release I have where 144hz is working is fglrx 15.10.4 and it seems to
work with every release there after.