Recent testing indicates that the M1 Mac Thunderbolt ports’ transfer speeds aren’t as fast as advertised by Apple. The good news is that this doesn’t affect the internal drive, which is typically the most used storage and, in some cases, the only storage some users access. However, the slower speeds could have a negative impact on professional video editors or anyone that relies on super-fast external storage for daily use.
External storage is often used to back up data if something goes wrong with the primary drive or the operating system becomes infected with a computer virus. In this case, a Mac computer’s Time Machine backup doesn’t need to be fast. What’s more important is reliability. In some cases, very slow media is used when there’s a need to store vast amounts of information. For example, some companies use magnetic tape drives to store petabytes of data safely offline at a relatively low cost. One petabyte is equal to a thousand terabytes which would cost hundreds of millions of dollars if stored on solid-state drives.
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While backup storage doesn’t have to be fast, some users require the highest transfer rates possible to keep up with demanding tasks such as editing video at 4K or 8K resolution. In some cases, the computer must simultaneously access multiple streams of this high-bandwidth content for transitions and picture-in-picture effects. That’s when performance that doesn’t meet claims can cause a problem. Recent testing by artist and Mac developer Howard Oakley of Eclectic Light Company revealed Thunderbolt port transfer speeds that were much slower than expected. While all M1 systems should support USB 3.1 Gen 2 at 10 gigabits-per-second, there appears to be some issue preventing the best bandwidth possible. In some cases, five gigabits-per-second was shown as the maximum, half of the rate expected. The good news is that USB 3.2 storage offered consistent 10 gigabits-per-second transfers even though Apple didn’t claim compatibility with this standard. USB 3.2 has a maximum transfer rate of 20 gigabits-per-second but only 10 gigabits-per-second.
M1 Mac Cables & Drives
Getting to the bottom of storage slowdowns is not an easy task. Various combinations of components must be checked in sequence to get a clear picture, and it seems like Oakley did a thorough job, calling in some help for verification from two other people. The factors that must be considered are the computer used for testing, the software used for testing, the ports being connected to, the cables used for the connection, and, finally, the external drives. If any of these fall below the rated standard, it will affect the results.
If these tests are accurate, the M1 Mac can’t achieve the full speed that should be possible when using USB 3.1 Gen 2. That’s disappointing, but there are some solutions. Using USB 3.2 storage connected directly to a Thunderbolt port on an M1 Mac reached transfer speeds of 10 gigabits-per-second, with read and write rates of about 910 and 970 megabits-per-second. That’s extremely fast and offers a solution for those with the most demanding applications. M1 Mac users with USB 3.1 Gen 2 drives, using a Thunderbolt 3 Dock, or the USB ports on a Studio Display, seem to offer better performance.