M1 Mac Thunderbolt Ports Do Not Fully Support USB 3.1 Gen-2: Report

A new report claims that most Thunderbolt 4 ports on Mac M1 computers don’t seem to support the full 10Gb/s transfer speeds that are part of the USB 3.1 Gen-2 specification.

Spotted by 9to5Mactesters at eclectic light found that several computers with M1 architecture ranging from the 2021 16-inch Macbook Pro M1 Max to the new Mac Studio have lower-than-expected transfer speeds when connected to external SSDs to the point that they don’t meet each other the standards that should be achievable via USB 3.1 Gen-2.

The current speeds offered by the different USB standards are as follows:

  1. USB 3.0 and later supports SuperSpeed ​​USB at 5 Gbps.
  2. USB 3.1 Gen 2 adds SuperSpeed+ at 10 Gbps.
  3. USB 3.2 adds two-lane SuperSpeed+ at 10 and 20 Gbps.

The Thunderbolt ports on M1 Macs support speeds of up to 40Gb/s, which is faster than USB 3.1 and USB 3.2, which would lead buyers to naturally assume that M1 Macs are able to get the maximum performance from the older USB 3.1 standard. . This test shows that this is not the case.

There’s a huge disparity (as well as significant confusion) caused by the different USB-C standards and the devices and cables they use. While Thunderbolt 4 should offer support for the other formats, in the case of M1 computers this does not appear to be the case.

Through multiple Thunderbolt 4 tests on M1 Mac Studio and M1 MacBook Pro machines, eclectic light found that the fastest external storage devices could only perform at about half of their expected speeds, with the best performance from an external storage device still operating at less than 10% of expected transfer rates.

“The only ports on Mac M1s that currently appear to fully support USB 3.1 Gen 2 are those on the front of the Mac Studio Max”, eclectic light said.

thunderbolt 4 ports on macbook

The report further claims that since the November 2020 launch, no Thunderbolt port in any M1 model appears to fully support the expected SuperSpeed+ 10 Gb/s (for SSDs). The biggest noticeable impact on speed comes from devices capable of approaching 10Gb/s rates such as RAID arrays and NVMe SSDs, where data transfer rates should be 900MB/s but seem to work faster. almost 500 MB/s.

“This flaw appears to have been present on all M1 Macs for almost 18 months. If this is a bug in the firmware of the fabric core(s) responsible, it should have been fixed over a year ago. If this is a defect in the M1 series chips, then Apple should have informed users and qualified its claim for compatibility of these ports,” eclectic light said.

“The lack of 10 Gb/s SuperSpeed+ support in USB 3.1 Gen 2 is arguably the most serious setback in what has otherwise been a very successful transition.”

PetaPixel contacted Apple for comment, but the company did not immediately respond. Full test results can be read on Eclectic Light.


Picture credits: Apple