Ultra High Speed (UHS) is a bus and speed class for SDHC (Secure Digital Card High Capacity) and SDXC (Secure Digital Extended Capacity) cards. These memory cards with large storage capacity are equipped with the fast UHS data bus, Ultra High Speed (UHS), to increase the data rate and are characterized by different UHS classes.
An important characteristic value of memory cards is the write and read speeds. In the case of SD cards, Ultra High Speed I (UHS-I), UHD-II and Class have been introduced as speed classifications that are shown on the nameplate. The SD cards SDXC and SDHC are available in the UHS-I version, which supports data rates of up to 104 MB/s via the UHS bus. Data rates of up to 312 MB/s are possible with SD cards with the UHS-II bus.
As for the nameplate, the bus information is in Roman numerals. As for the UHS classification, this value indicates the speed between the device and the memory card. The specifications for the UHS class and the data transfer are entered in a U-shaped symbol in Arabic numerals.
The UHS bus comes in two classes: UHS-I has a maximum data rate of 104 MB/s and UHS-II has one of 312 MB/s. As for the UHS class, this value indicates the minimum speed between the device and the memory card. The higher the digit of the UHS class, the higher the transferable data rate. The Secure Digital Association( SDA) has defined four UHS classes: Class 2 with 2 MB/s, Class 4 with 4 MB/s, Class 6 with 6 MB/s and Class 10 with 10 MB/s. The UHS bus and UHS speed class designations apply equally to SDHC, miniSDHC, microSDHC, SDXC and microSDXC.
To operate the SD cards, the specifications for the UHS versions and UHS classes must be met by the memory card and the device.