Bus Speed (Default Speed/ High Speed/ UHS)

Bus Speed

For the sheer variety of high-performing, feature-rich devices, the SD Association introduced higher speed bus interface (I/F) and its Maximum writing speed specifications for SDHC memory cards and SDXC memory cards.

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
(SDR50, DDR50)
104MB/s (SDR104)
UHS-II SDHC and SDXC 156MB/s Full Duplex
312MB/s Half Duplex
UHS-III SDHC and SDXC 312MB/s Full Duplex
624MB/s Full Duplex

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.

UHS-II and UHS-III Pin Layout

A new pin layout introduced to support the UHS-II bus interface also supporting UHS-III. The second-row pins on the full-size SD memory card and microSD memory card are used for the UHS-II and UHS-III bus interface signals. The first-row pins are used for the conventional normal speed, high speed and UHS-I bus interface signals to provide interoperability with those conventional interface host devices.


UHS-II and UHS-III Pin Layout