4 M5 Ultra Mac Studios Hit 4.8TB/s Memory Bandwidth

EXO Labs has been working with Apple for a year to develop a way to link Macs into an AI cluster. Their approach uses RDMA over Thunderbolt 5, which lets data move directly between memories without going through the OS or CPU. This is what allows the memory bandwidth of four machines to add up to roughly 4.8TB/s.

The M5 Ultra chip, also announced on the same day, provides up to 36 CPU cores and 80 GPU cores, with a memory bandwidth of 1.2TB/s per chip. By scaling bandwidth almost linearly with the number of devices, the cluster can run large language models like Kimi K3 and GLM-5.3 at what the company calls "API-like speeds" locally. Apple has also featured this capability on its Mac Studio product page, suggesting official recognition of the use case.

For business readers, the significance lies in running very large models on-premises rather than relying on cloud APIs. The main trade-off appears to be cost and hardware setup time, given the ¥949,800 starting price per machine. The late-October availability of the 512GB model suggests that maximum memory capacity may be the more relevant configuration for this type of workload.