Would double check all connections & cables - gigabit speeds are only reachable on 4 twisted pairs properly connected (so all 8 wires) - if even 1 wire connection is spotty, connection falls back to 100mbps which can be reached on 2 twisted pairs (4 wires)
Could be that during/after your upgrade activities, one of the wires in one of the connectors got "dislodged". this will be far more likely than a driver issue. Maybe try with a laptop on the same cable to doublecheck
Of course, if you only ever get 100mbps no matter the cable or ports/devices you are plugging it in to, the board could also be at fault, RMA needed.