The new M1 Macs from Apple have a persistent Thunderbolt Port issue. It is the primary reason for slow speed while trying to transfer data from M1 Macs to an external storage device. Apple is still mum about the slow transfer speeds on these devices, even after 18 months since their release.
Slow Data Transfer Speed of M1 Macs
Researchers at Eclectic Light conducted a detailed experiment to document the data transfer speeds on M1 Macs. However, the tests revealed that the M1 Macs failed to reach the stellar data transfer speeds advertised that the standard is usually able to attain.
The experiment involved two M1 Macs. An Apple Mac Studio with M1 Max and an Apple MacBook Pro 16-inch, 2021 with an M1 Pro processor. Both of these top-tier devices were connected to multiple external SSDs which support USB 3.1 Gen 2.
Eclectic Light used certified cables in its data transfer speed experiment. Both the devices were running macOS Monterey 12.3.1 with Full Security mode. They even tested the cables with an Intel Mac to verify that they support the USB 3.1 Gen 2 standard.
Advertised Data Transfer Speeds
Apple advertises that M1 Macs support USB 3.1 Gen 2 standard. It means theoretically, data transfer speeds can go up to 10 Gb/s. However, the actual speeds of the USB 3.1 Gen 2 standard lie between 1100-1200 MB/s. But these test devices are nowhere near that actual data transfer speed range.
The results weren’t as promising as claimed by Apple in its product specifications. In general most of the USB Type-C ports and ThunderBolt 4 ports recorded speeds lower than 500 MB/s. The read speeds lay between 386 Mb/s and 406 Mb/s while write speeds were between 430-435 MB/s.
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The biggest disappointment was the front USB port of the Apple Mac Studio with M1 Max. It registered a horrible 20 MB/s read and 37 MB/s write speed. Only the USB 3.2 storage which was connected directly to a Thunderbolt port on an M1 Mac produced good results. The front USB Type-C port of the Mac Studio is the worst performing port on the test devices.
Howard Oakley, the researcher behind this experiment, recommended a few solutions in his blog post. He advised using the Thunderbolt 3 docks or the USB ports on the Studio Display. He added that Apple should not promote misleading read and write speeds and should work on fixing this issue.