I'm at my wits' end with this new PC build! No matter what I try, my Ethernet connection is locked at 100 Mb/s, and my Wi-Fi barely hits 120 Mb/s. Other devices on the same network, including my laptop and phone, consistently get speeds between 400-600+ Mb/s on Wi-Fi and 650-700+ Mb/s on Ethernet.
I've gone through so many troubleshooting steps over the last six hours, including:
- Using three different brand new Cat-6 cables
- Directly connecting to the modem (Spectrum EN2251 DOCSIS 3.1)
- Fully power cycling the modem
- Updating and switching BIOS versions
- Clearing CMOS and discharging the board
- Fresh installs of Windows 11 and Pop!_OS
- Trying multiple Realtek drivers
- Disabling various power-saving features and forcing 1.0 Gbps Full Duplex
- Testing different ports and devices, which all work fine.
Here are my build specs:
- AMD Ryzen 9 9900X3D
- MSI MAG X870E Tomahawk WiFi (Realtek RTL8125B 2.5Gb Ethernet, Qualcomm FastConnect 7800 Wi-Fi 7)
- 64GB G.Skill Trident Z5 Neo DDR5-6000
- Gigabyte RTX 5080 Aorus Master
Nothing seems to work, and I'm frustrated! I don't want to RMA it if there's a fix I can apply. Does anyone know if the RTL8125B might have a hardware defect, or could it be something like a bad jack or firmware issue? I just want to get my dream rig running properly!
5 Answers
I've noticed the same thing. When I plug into the motherboard, Windows shows speeds at 100/100. But using a dongle, I hit 1000/1000 with full speeds. Looks like there's something off with your board!
It sounds like you may have a bad network interface card (NIC). If your other devices are getting gigabit speeds on the same cables and ports, the RTL8125B might be faulty. Instead of going through the hassle of an RMA, I suggest buying a PCIe NIC for about 30 bucks. It's a quick and easy fix!
If you've tried everything and it’s still stuck, just replace the motherboard. I switched to an Asrock B650E PG Riptide WiFi, and it fixed everything for me.
Have you updated your chipset drivers? Also, if you're using an MSI board, be cautious with the Killer network software. It can sometimes mess with your speeds. Just a thought!
Check your NIC settings in Device Manager. Make sure it’s set to "Auto Negotiation" for the best speed. You should also check if it’s stuck on 2.4GHz for Wi-Fi. If all else fails, a new NIC or even a USB Wi-Fi dongle could do the trick. And don’t forget to check for any damaged pins in your Ethernet port—sometimes it only takes one to mess things up.
A USB-C to Ethernet dongle boosted my speeds to 600+.
I've been there! I had a similar issue with an older machine. I tried everything too, replaced cables, switched ports, you name it. Finally, I just bought a 2.5 gig PCI card, and it solved my speed woes instantly. Worth it!