I installed a new ASUS TUF B850i Neo motherboard, but my wired connection only reaches around 750–800 Mbps on a 910 Mbps internet plan. My phone reaches the full advertised speed over Wi‑Fi, so I'm wondering why Ethernet is slower.
I've already reinstalled the latest network drivers, confirmed that Windows reports a 1000 Mbps link speed, tried another cable, and disabled Gigabit Lite and Energy Efficient Ethernet in the adapter settings. I also didn't reinstall Windows after changing the motherboard. Could that be causing the problem, or is there another setting or hardware limitation I should check?
3 Answers
Try testing the local network separately with iperf3. That removes your ISP and the internet speed-test server from the equation. If iperf3 shows close to gigabit performance, the Ethernet adapter and cable are working correctly and the limitation is probably somewhere between the router, ISP, or speed-test setup.
As another troubleshooting step, temporarily disable Quality of Service or traffic-prioritization features on the router and PC. QoS can sometimes limit throughput, although the router’s WAN/LAN port speeds are the first thing I’d verify.
Those results aren’t necessarily a sign that the motherboard is faulty. A 1 Gbps Ethernet link usually tops out around 930–950 Mbps after protocol overhead, and other network traffic can reduce a speed test further. Also, Ethernet cables marketed as Cat8 are uncommon, but a good Cat5e or Cat6 cable is already sufficient for gigabit.
The difference with your phone may be because your router’s Wi‑Fi is connected through a faster 2.5Gbps WAN link, while its wired LAN ports may only be 1Gbps. Check the router’s port specifications. Reinstalling Windows probably isn’t necessary.
The reason I’m concerned is that the phone gets a higher result over Wi‑Fi. I expected the PC’s wired connection to at least match it.