SD Bus Interface Specification has been continuously increased over the years from High Speed (25MB/s) to 3rd Generation of Ultra High Speed UHS-III (624MB/s). Now the SDA offers SD Express which use the PCIe  Gen.4 Interface with NVMe Protocol to deliver (3940MB/s) data transfer rates between SD host devices and memory cards.

See “SD Express – Revolutionary Innovation for SD Memory Cards” in Youku.

See video for application advantages
Bus Speed

Any high speed cards can be used in UHS-I, UHS-II or SD Express host devices.

In order to utilize the performance supported by a host device it would be desirable to use cards that supports the highest speed interface supported by the host. Therefore, devices supporting UHS-I perform the best with cards that support at least UHS-I.

UHS-II host devices perform the best with cards that support at least UHS-II and SD Express host devices will perform best when using SD Express cards.