Getting 25 Gbps Thunderbolt Ethernet on My Mac Studio

A Mac Studio user sought to upgrade their workstation to support a faster 25 Gbps Thunderbolt Ethernet connection, as their existing 10 Gigabit Ethernet was not meeting their needs. After researching options, they discovered a cheap 25G Thunderbolt adapter utilizing a server-pulled OCP 2 NIC with a Thunderbolt 3 adapter board. At a price of $160, the adapter seemed like a good deal, and they proceeded to test its performance.

The user faced two issues while testing the adapter: the iperf3 tool on their NAS was outdated, limiting the bandwidth to 15 Gbps, and the adapter enclosure was overheating. They resolved the first issue by updating iperf3, achieving a speed of 20 Gbps. However, the adapter remained hot, so they decided to improve its cooling.

The user designed a custom fan duct and printed it using Noctua beige PLA to fit the adapter enclosure. They added a low-profile heatsink and a speed-controlled USB fan, securing everything together with screws from the adapter enclosure. After assembling the cooling system, the NIC temperature dropped to under 36°C after 10 minutes of testing.

Despite the cooler temperature, the adapter's maximum speed remained around 20-25 Gbps due to the Thunderbolt 3 chipset's limitations. Real-world testing revealed that the adapter provided only a marginal improvement over the built-in 10G Ethernet, with file copy speeds of around 1.4 GB/sec read and 1 GB/sec write. The user concluded that the effort and cost involved in upgrading the adapter may not have been justified, especially given the slower performance of their low-power Arm NAS.