Framework's 10G Ethernet module shows how uneven USB-C bandwidth is

A 10-gigabit card for Framework's expansion slots

WisdPi has been building 5 Gbps and 10 Gbps Ethernet adapters for a few years, using newer Realtek chips that sometimes behave inconsistently, most often under Linux. Its latest product, the WisdPi 10G Ethernet Expansion Card, fits any free Framework Expansion slot, including on the Framework Desktop. Jeff Geerling tested it in a video and a blog post, and the result is a clear lesson in how much USB-C bandwidth varies from port to port.

The core issue is that the card relies on the Realtek RTL8159 controller, which needs USB 3.2 Gen 2x2 — 20 Gbps — to reach its full rated 10 Gbps. The real-world peak is around 9.4 Gbps. On many Framework laptops, users will get considerably less.

Measured throughput: 7.4 Gbps, then 9.4 Gbps

On a Framework 13 with AMD's Ryzen AI 5 340, Windows 11 averaged about 7.4 Gbps, and Linux did slightly worse, even though Framework's own port documentation lists USB 3.2 Gen 2x2 support for ports 1 and 3 on that machine. The RTL8159 is bottlenecked on many USB4 connections and on all USB 3.2 Gen 2x1 links, which caps bandwidth below 8 Gbps.

A Framework 12 with a 13th-generation Intel mobile CPU should support Gen 2x2 as documented. In Linux the port did report 20,000 Mbps through lsusb, but iperf3 delivered only 7 Gbps, and the Realtek driver failed to compile on Ubuntu 26.04, apparently because that distribution's 7.x kernel is too new. Switching to Windows 11 and installing the Realtek driver finally produced the expected 9.4 Gbps. A bidirectional test gave roughly 9 Gbps upstream and 4–5 Gbps downstream.

Heat, size and the case for 2.5 Gbps

After sustained testing the module became very hot: close to 70°C on its bottom plastic surface, warm enough to cause toasted skin syndrome with prolonged contact. WisdPi told Geerling the surface temperature complies with IEC 62368-1 safety limits, as long as skin is not in contact with it for more than 10 seconds. Since the card sticks a couple of centimetres out of the laptop and has to be removed before the machine goes into a sleeve, the advice is to use it where it will not sit on your lap.

For most people, the recommendation is the standard Ethernet Expansion Card, which handles 2.5 Gbps for about $40. The $99 WisdPi 10G card only makes sense for those who need more speed and want to avoid an external USB-C dongle — and at the time of writing it was out of stock. WisdPi sent the review unit to the author.