Getting 25 Gbps Thunderbolt Ethernet on My Mac Studio
Points and comments are a snapshot, not live.
A blogger modded a cheap Thunderbolt 3 adapter for 25 GbE on a Mac Studio.
Jeff Geerling upgraded his Mac Studio to 25 GbE using a $166-$299 Thunderbolt 3 adapter with a server-pulled OCP 2 NIC, cheaper than $999+ alternatives. The NIC overheated in its passive enclosure, so he designed and 3D-printed a fan duct for a Noctua 80mm fan, soldered to the PCB for 5V power. Real-world Samba file transfer speeds reached ~1.4 GB/s read and ~1 GB/s write, limited by Thunderbolt 3 and SMB overhead, only marginally better than the built-in 10G.
Bandwidth in iperf3 hit 20-25 Gbps, limited by the Thunderbolt 3 chipset.
What commenters are saying
Commenters noted the real bottleneck likely is macOS lacking SMB Direct (RDMA) support, not the hardware. Several pointed out Apple added RDMA support in March 2026, but the SMB driver hasn't been updated to use it, so the protocol remains the limit. Others shared experiences: one runs a similar setup using a cheap eGPU dock and PCIe card, reporting similar speeds; another emphasized that macOS SMB is historically unreliable, recommending nsmb.conf tweaks or running Linux in a VM for better performance. A separate thread discussed USB-C/Thunderbolt networking as a cheaper alternative for point-to-point links.