slow broadband speed from PC's ethernet port

I have a 8 y,o laptop with a built in ethernet (RJ45) port. When I connect a LAN cable to it, the speed tests shows 300+ to <400 Mbps. I have already tried to update the driver. Using the same cable and LAN connection, I get up to 900+ Mbps when I connect through an (external) USB 3 ethernet adaptor. What can I do to obtain improved speed through the built in ethernet port? PS PC runs Windows10 Home