USB Gigabit Ethernet Adaptor is stuck at 10MB/s


I have installed the USB 2.0 Gigabit Ethernet Adaptor on three computer/laptops running Win XP and Ubuntu 11.10 & 10.10, and the maximum speed I was able to clock was between 10 to 11 MB/s while copying 4 GB file from a SAN share on a gigabit network. On the otherhand, when I test with another PCI ethernet card, I’ve clocked between 60 to 80 MB/s. I am aware that since this is a USB 2 the max I will expect is 480Mps and not 1000Mbps but I am getting way low readings; almost close to the 100 Mbps card that I already have.

It should be noted that my current network uses CAT6 cables & NetGear Gigabit Switch; and my OSs (Ubuntu and XP) reported a status of 1000Bps for the ethernet’s speed.

I appreciate any feedback; many thanks in advance


Hi AbuSous2000,

Thanks for you post, we’ll be happy to help. You are correct that USB 2.0’s speed limitations will be the bottleneck on the USB to Gigabit ethernet but the numbers you are reporting are quite low. Because of the complexity of network environments it’s difficult to pinpoint exactly where the hangups are.

In the meantime, can you verify the speeds you are seeing making sure to use the same cable into both the USB and PCI ethernet ports (connecting the same to the NAS) and perform the same copy/transfer test?

Although we don’t have an identical setup to yours, we are doing some testing here to see how much we can optimize the transfer rates
I’ll let you know as soon as we have a better idea of our next steps.
Thanks for your patience while we figure this out.


Plugable Technologies


Hi Jerome,

I have changed the CAT 6 to another CAT 6, and there was little imporvement (around 20%). I clocked between 12 to 16.8 MB/s.


Hi Jerome,

I just tested with iSCSI Target within SAN, and it clocked between 15 to 18 MB/s, but with CIFS/share no more than 12MB/s. Alsi it should be noted that CPU utilization was under 5%, same thing goes for memory as well, under 5%


Hi Again AbuSous2000,

Sorry for the slow reply. I’m still working on getting you some definitive answers about the kinds of numbers we can expect from the USB to Gigabit Ethernet on OS X 10.7.3. So far the numbers look about the same as with 10.7.2, and I haven’t observed any version problems.

Basically the Gigabit ethernet is at least twice as fast as 10/100 interfaces. What I’m still working on is removing all of the caching and protocol overhead to get closer to maximum numbers.

Also, I’m testing multiple units to see if there’s evidence of any failing in a way that makes the performance suffer. Usually what we see when they fail is either the device not being recognized by the system or, being recognized but not working at all. I’ll keep working on it and let you know what I find.

Thanks for your patience,

Plugable Technologies


great to know that I am not being ignored; that means a lot to me


Hi Abu,

We’re definitely not ignoring you! We’re just wanting to make sure we can give accurate, valuable advice. Feel free to contact us at and if your device isn’t something you want to live with. Otherwise, we’re still working on getting a good test setup to eliminate as many of the network overhead variables as possible. Sorry for the delay…

Thanks for your patience,

Plugable Technologies


I am willing to wait; you have a good and promising product and I like to help you. Please let me know if you like me to do kind of testing.

Are you able to duplicate in your enviornment? I am almost sure somebody esle will run into this.

if you are not able to duplicate I can mail to you and you send me another one.

I appcaite the attention
Please advise;


Hi AbouSous2000,

Sorry for the long delay, I finally have some numbers for you. What I did to characterize the performance of the USB to Gigabit ethernet adapter is as follows:

Using iperf on two computers connected directly with a cat 5e ethernet cable one from one on-board PCI Gigabit ethernet controller to a USB to Gigabit ethernet controller. I then compared the results of this test to results between two on-board PCI Gigabit controllers.

The USB to Gigabit ethernet adapter transferred at a bit over 200 Mbits / sec. This is about what’s expected because of USB overhead and the limit of USB, still quite a bit less than 480, but quite a bit higher than what you reported.

PCI to PCI was in the 700 - 900 range, again, as expected.

With this as a baseline, I wonder if it would be possible for you to get something like iperf going (‘sudo apt-get install iperf’ on ubuntu) and connect two of your machines directly temporarily by-passing the network, and see if you are getting numbers in the 200 Mbit / sec range.

If so, we can work to figure out what’s going on between the adapter and the NAS, but if not we’ll get you a pre-tested replacement to rule out hardware as a cause of the slowness.

Let me know if this works for your and what you find.

Thanks for your patience,

Plugable Technologies.


Give me couple of days and I will get back to you. many thanks in advance


The best I got was 17 MB/s, I guess that 136 Mbps

It should be noted that was the case going after the NAS iSCSI, if go after the NAS with CIFS the best I got was 12 MB/s.

Also note that on the same SAN via iSCSI I get 110MB/s when I used PCI Gigabit Ethernet card.

If you or others can do better, please let me know. But for now, I am giving up. I guess this is the best I am ganna have; too bad I was expecting more.


Hi Again,

We compiled our test results and posted them available here:…

While we can’t recreate your setup exactly, this should give you an idea of some baseline performance numbers you can expect and the details on how to perform the same test on your systems.

Let us know if you get similar results running iperf with isolated ethernet connections, then we can begin to add network components back in and see where the perfornance begins to degrade.

Thanks for your patience,