USB Gigabit Ethernet speed on Mac OS X

USB to Gigabit Ethernet adapters are especially useful for adding faster wired network capability to otherwise WiFi-only machines like the Macbook Air.

You can buy Apple’s branded 10/100 USB adapter — but price-wise, it will cost more than some gigabit adapters (like our Plugable USB Gigabit adapter). A gigabit adapter is also a nice upgrade for machines that only have a 10/100 ethernet port, but are connecting to a gigabit-capable network.

Because there’s often confusion about the rated speeds and actual throughput, especially when running 1000Mbps Ethernet over USB 2.0’s 480Mbps bus, we did some testing to establish a base line.

The test:

We installed the latest ASIX AX88178 Mac drivers for the Plugable Gigabit Adapter (currently v6.3.0). We used the open source network testing tool iperf running on a Mac Mini Server running 10.7.3 and a MacBook running 10.6.8. If you’d like to duplicate our tests, here’s a nice pre-compiled GUI version available here: JPerf-2.0.2.dmg. In order to isolate the adapters as completely as possible, we connected directly between two ethernet ports, set the address manually and ran iperf as both server and client in each direction. Remember that in order to get gigabit speeds, your entire network (including any routers in-between) need to be gigabit capable.

The results:

PCI-Gigabit Ethernet
940/936
USB-to-Gigabit Ethernet (Plugable USB2-E1000)
250/320
USB 10/100 Ethernet
94/94

* send/receive speeds to a 2nd machine running PCI Gigabit Ethernet

These are low-level performance numbers (raw TCP/IP throughput). Real world throughput like copying a file over the network will be substantially lower due to transport overhead and any bottlenecks on the network or on either side of the transfer.

Using a tool like iperf and isolating the ethernet adapters to a direct connection establishes a base line for data speeds. To further identify potential networking bottlenecks, introduce one network component at a time and rerun your tests to see how the throughput is effected by the increasing complexity.

For detailed instructions on installing Mac drivers for the Plugable USB2-E1000, see Howto: Installing ASIX’s USB Gigabit Ethernet Driver on Mac OS X Lion 10.7.

We hope these numbers are useful to set performance expectations. Have any questions? We’d be happy to help. Reply here or email support@plugable.com anytime. Thanks!

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