I decided to test my new NVMe drive speed and was astonished how slow it was 42mb/s. I tried a different cable same result. So then I tested the same drive with a thunderbolt 3 to USB adapter and it was 400+ mb/s. This is a 2019 iMac with i9. Anyone know what might be going on?
Are you sure the drive is Thunderbolt 3 (lightning bolt icon on the connector), not just USB-C. If you use a Thunderbolt 3 cable with a non-Thunderbolt USB-C device, it may run at USB 2.0 speeds, which would explain your 42MB/s.
If the connector has no lightning bolt icon, use a USB-C 10Gb/s cable, not Thunderbolt 3. For short cables (0.5 m) they are the same, but not for longer cables.
Are you sure the drive is Thunderbolt 3 (lightning bolt icon on the connector), not just USB-C. If you use a Thunderbolt 3 cable with a non-Thunderbolt USB-C device, it may run at USB 2.0 speeds, which would explain your 42MB/s.
If the connector has no lightning bolt icon, use a USB-C 10Gb/s cable, not Thunderbolt 3. For short cables (0.5 m) they are the same, but not for longer cables.
Hello,
Please reach out to the drive’s manufacture for further assistance.
New NVMe drive is slow on thunderbolt 3
