Users of Mac computers with M1 are reporting an issue that they did not expect when they purchased these models from Apple. Transfer speeds are very slow with external SSDs. Testing seems to show that most of the Thunderbolt ports on these models aren’t compatible with USB 3.1 Gen 2, meaning they don’t offer the maximum 10Gb/s transfer speeds you’d initially expect. The tests that have been carried out prove it. To say that they have been made on a 16-inch MacBook Pro M1 Max 2021 and a Mac Studio M1 Max 2022.
Putting theoretical versus actual speeds aside when it comes to analyzing transfer speeds, most M1 Macs don’t support the USB 3.1 Gen 2 standard, which makes Thunderbolt transfers slower than expected. what they should be, both in theory and in practice. This is a fact and not a theory. A verifiable fact Tested on a 2021 16-inch MacBook Pro M1 Max and a 2022 Mac Studio M1 Max.
The theoretical standards are as follows:
- USB3.0 onwards supports USB transfers at 5 Gb/s.
- The 3.1 Gen 2: 10Gb/s.
- 3.2 reaches 10 and 20 Gb/s.
Tests conducted by Howard Oakley of Eclectic Light, suggest the following:
- storage devices faster ones run at about half the expected speeds.
- The limitation appears to be present on all M1 Macs. Using a Thunderbolt 4 cable used to connect a USB-C device to a Mac Studio, results in speeds less than 10% of those expected.
- The latest Mac Studio models do not support USB 3.1 Gen 2.
- No Thunderbolt port on any Mac model with M1 It seems to be fully compatible with 10Gb/s SuperSpeed+, at least for SSDs.
- For SATA/USB-C storage, the performance impact is limited, reducing transfer speeds 500MB/s to 400MB/s
- Users with USB 3.1 Gen 2 devices they must be connected to a Thunderbolt 3 dock.
