UHS-I, UHS-II, and UHS-III are speed classes for SD cards, defined by the Ultra High Speed (UHS) bus interface. These standards determine the cards' maximum data transfer rates and performance capabilities, catering to different levels of demand in photography, videography, and other high-speed applications.

UHS-I: Introduced in 2010, UHS-I was the first UHS standard, offering a significant leap in speed compared to non-UHS cards. It has a theoretical maximum transfer rate of 104 MB/s using a single row of pins. UHS-I cards are widely used in consumer devices like cameras, drones, and smartphones, providing sufficient speed for HD video recording and general-purpose storage.

UHS-II: Released in 2011, UHS-II doubled the pin count to two rows, enabling faster data transfer. It has a theoretical maximum speed of 312 MB/s. UHS-II cards are backward compatible with UHS-I devices but require UHS-II-compatible hardware to achieve their full potential. These cards are ideal for 4K video recording, burst-mode photography, and professional-grade applications.

UHS-III: Introduced in 2017, UHS-III increased the maximum transfer rate to 624 MB/s, using the same dual-row pin configuration as UHS-II. It is designed for advanced applications like 8K video recording, high-resolution continuous shooting, and high-performance computing. However, UHS-III adoption has been limited, as newer technologies like SD Express have emerged.

The key differences lie in their speed capabilities and compatibility. UHS-I is the most common and affordable, while UHS-II and UHS-III offer progressively higher performance for demanding tasks. However, to fully utilize UHS-II and UHS-III speeds, compatible devices are required. Despite their advancements, UHS-III has seen less adoption due to the rise of even faster standards like SD Express, which leverages PCIe and NVMe interfaces for speeds exceeding 985 MB/s.

Tag：UHS,SD