If you've got a Mac Studio and a spare Mac mini and you've wondered whether chaining them gets you a bigger model, the answer changed in December and most of the advice out there hasn't caught up. Three things get called "Mac clustering" and they're not alternatives. They stack. At the bottom is RDMA over Thunderbolt. It's not software you install, it's a macOS capability. One Mac reads another's memory directly, without the OS copying it through a network stack. macOS 26.2 or later, Apple silicon, Thunderbolt 5. Apple's technote TN3205 has the requirements. In the middle is MLX, Apple's own framework, which actually runs the model. Its distributed layer has two backends and the backend IS the strategy. On top is EXO, which finds your machines and decides how to split the work. It runs on MLX. You can skip it entirely if you want to write a host file yourself. Here's what I think most people are getting wrong. There are two ways to cut a model across machines. In a relay, each machine holds a block of layers and work passes down the line, so one machine computes while the others wait. More machines, bigger models, no extra speed. That was the only option for years, and it's where "clusters are for capacity, not speed" comes from. That advice was correct. In the other mode, every machine holds a slice of every layer and they all compute at once. The work divides. It needs hundreds of synchronisations per token, which only became viable when the fast link shipped. Exo Labs publishes up to 1.8x on two devices and 3.2x on four. The result I find most convincing isn't a benchmark. Jeff Geerling ran two programs on the same four Macs with the same cables. One sped up as he added machines. The other slowed down. Same metal, opposite direction. Two things worth knowing before you spend anything. The feature ships switched off. You enable it from Recovery mode with one command, on every machine. Miss one and nothing fails, no error, no warning. The cluster just runs the slow way and you conclude the technology is overhyped.