How fast can you copy 1 TB over Thunderbolt 4? Peak SSD speed limitations

How this is calculated

In practice, Thunderbolt 4 is rarely the bottleneck. Modern NVMe-based Thunderbolt 4 enclosures sustain ~28 Gbps (3.5 GB/s) write speeds, so 1 TB takes closer to 5 minutes in real use. Hitting the full 3m 20s requires both a top-tier drive (Samsung 990 Pro class) and a system that can feed data that fast from the source. USB 4 (also 40 Gbps) performs identically for this transfer. Thunderbolt 5 bumps to 80 Gbps symmetric, cutting the theoretical time to 1m 40s.

Verdict

1 TB at Thunderbolt 4's 40 Gbps peak works out to 3 minutes 20 seconds, about 8x faster than USB 3.0's 5 Gbps for the same file, and that gap is why Thunderbolt's pitch has been 'external storage that's as fast as internal' for the past decade. In practice sustained throughput on a fast external NVMe SSD hits 2.5-2.8 GB/s once DisplayPort tunneling, the ~32 Gbps of usable PCIe 4.0 x4 bandwidth, and protocol overhead take their cut, so the same 1 TB lands closer to 4-5 minutes on a real-world run. The verdict's use-case framing is precise: high-end video edit workflows and overnight SSD backups are exactly the transfer pattern where 3-5 minutes per terabyte is the difference between routine and weekend-task, where USB 3.0's 35-60 minute per-terabyte math makes the same backup a chore rather than a coffee-break task.