SD Association

Bus Speed

Because of the variety of high-performing and feature-rich devices in the market, there is a demand for higher performance SD memory cards. The SDA has introduced a higher bus interface with higher theoretical read and writing speed specifications for the SDHC standard and SDXC standard.

Bus Interface Card Type Bus Mark Bus Speed Spec Version
Normal Speed SD, SDHC and SDXC --- 12.5MB/s 1.01
High Speed SD, SDHC and SDXC --- 25MB/s 2.00
UHS-I SDHC and SDXC 50MB/s (SDR50, DDR50)
104MB/s (SDR104)

*Maximum speed differs from the bus I/F speed. It varies depending upon the card performance. The average speed that a device writes to an SD memory card may vary depending upon the device and the operation it is performing. The speed may also depend on how other data is stored on the SD memory card.

Normal and high-speed cards can also be used with UHS-I host devices, but the high performance enabled by a UHS-I host device can only be achieved with a UHS-I memory card.