I have a Realtek Gaming GbE Family Controller. I've just upgraded all cabling to Cat 6. I've set 1.0 Gbps Full Duplex in the Controller Properties (from Auto Negotiation), and I've got into my router and confirmed that it has a 1000Mbps connection. I downloaded the Realtek driver from the Realtek page. The speed still registers as 100 Mbps in the Ethernet Status dialog on Win 10.
Does anyone have any other ideas? I've looked at numerous forums (including this one) and can't find any other suggestions.