I am using “Cable Matters® SuperSpeed USB 3.0 to RJ45 Gigabit Ethernet Network Adapter” plugged into USB 3.0 port of Lenovo U410 laptop (Windows 8.0)

When speed tested on speedtest.net, it only shows speed 85-95Mbit. In my office network is 1Gbit (tested, shows 700-800Mbit connection with other computers).

My laptop has 100Mbit card in it, so when I use native RJ45 port, speed is 100Mbit again.

Also, I tested it on MacBook Pro with Mac OS X 10.10 (Yosemite), and there speed also limited to 90Mbit.

I looked through google, but nobody seems to raise this issue. It is not issue with USB 2.0 port pretending being USB 3.0 because USB 2.0 should allow up to 500Mbit connection.

I wonder whether that is an issue with drivers (I installed from CD coming with unit), item itself, or just false advertisement.

UPDATE Cables and ports are important for connecting to ethernet. However, it seems that the device is either faulty or doesn't work at all by design. Also I couldn't find any success stories where people used it to get 1Gbps speeds. I couldn't on my Win8 or MacOS X machines.

  • 3
    Does you patch cable have all four pairs (8 wires) connected on both ends? – Ron Maupin Oct 23 '15 at 22:52
  • 3
    Make sure the cable you are using is gigabit capable. – David Schwartz Oct 23 '15 at 23:11

If the USB adapter’s driver software, and the switch port to which your computer connects, are truly 1 Gb ports set to auto-detect port speed, or set to 1 Gb, the problem likely lies in the cabling: Either your patch cable—the horizontal cable—or the switch patch cable doesn’t have all four pairs connected on both ends.

Gigabit Ethernet requires all four pairs, while 100Mb only requires two pairs. Gigabit ports will drop to 100Mb when they don’t have all four pairs to use through the entire cable path because the 1Gb negotiation fails, and it falls back to 100Mb.

  • I tested a bit more. I have two RJ45 sockets under the desk, one allows my macbook to run at 100Mbps, another -- at ~800Mbps. So cabling/socket issue is cleared. But my Win machine is still only runs at 100Mbps. I am looking into different drivers for USB3->1Gbps Ethernet under Win8 now. – aaaaa says reinstate Monica Oct 25 '15 at 5:13
  • My macbook does detect full-duplex with given cable/wall port, giving 1Gbps connection. When I went to properties of the USB-Ethernet device and set it to 1Gb/full-duplex, it rebooted (device only) and stop working all together. For info: it is setting in Network center -> Connections: Ethernet ->Properties -> Configure -> Advanced -> Speed&Duplex – aaaaa says reinstate Monica Oct 25 '15 at 5:34

I wonder whether that is an issue with drivers (I installed from CD coming with unit), item itself, or just false advertisement.

Never trust the drivers on CDs that come with devices since many times those drivers on the CD are usually out of date. Checking the official Cable Matters® website shows various different driver download options.

And the site that site then points to—who I assume are the OEM manufacturers—has a fairly huge list of drivers for the “AX88179” which I assume is the actual OEM part number for the adapter you have.

Specifically I am looking at this Mac OS X driver that was released on August 20, 2015:

And there are other drivers for other platforms that seem to be similarly updated.

  • unfortunately, different drivers didn't help – aaaaa says reinstate Monica Oct 25 '15 at 5:48
  • @aaaaaa Sorry, but no other idea what might be up especially if cabling is fine. Could be a defective unit? – Giacomo1968 Oct 25 '15 at 5:56

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