why does usb 2.0 to gigabit ethernet adapter only work at 100 mbps on laptop running win7?

Have disabled onboard lan port. E-1000 still runs at 91.437 mbps.

Hi George,

Thank you for posting about your adapter.

As you probably know, there are many factors that can affect speed. Typically if the adapter has a problem, it shows up as a total failure rather than a speed reduction.

In testing under ideal conditions here at Plugable, we see about 250-300 Mbps on this adapter.

Although USB 2.0 is supposed to support up to 450 Mbps, realistically the number tends to be closer to 400 or even less at the port, and that is raw bits, some of which are used for headers, messages back and forth and other TCP/IP and USB overhead.

I’m sure you have already consulted with your ISP about the maximum speed they guaranteed, and why you aren’t seeing it. Sometimes we find that these guarantees can be somewhat optimistic, and are especially less reliable on cable-based systems when there is a peak load or an annoying neighbor with a spam-bot or a illicit server on his computer hogging bandwidth.

Other things to check is to make sure that all cabling and devices between the computer and the router and the router itself are gigabit compatible. When testing, make sure no other computers are active on the network. If possible, connect directly to the router, and be sure to turn of any other applications that use the network, including background apps.

With an older laptop, it could be that the CPU is struggling to maintain a higher speed, and it is possible for older computers to accumulate malware over time that can hook into the network stack and cause problems, if not actively uses it to connect with an illicit server.

I hope this gives you some clues to figuring out what might be wrong.

Thank you,

Plugable Support

Hi George,

We are going to close this thread. If you have any further questions, please contact us directly at support@plugable.com. Thanks!