Panduan Kelas Kecepatan untuk Kartu SD dan microSD

UHS Speed Class

The next speed class up is the UHS (Ultra-High Speed) Speed Class and it’s denoted with the “U” symbol. There are two ratings within the UHS Speed Class:

• U1 (UHS Speed Class 1): minimum write speed of 10MB/s
• U3 (UHS Speed Class 3): minimum write speed of 30MB/s

The UHS Speed Class is more commonly used nowadays than the Speed Class and many of the high-end cameras require at least a U3-rated memory card for many of its functions like recording high-resolution videos. The UHS Speed Class mainly refers to the minimum sustained writing performance for recording videos and came about due to 4K-capable video recording devices needing faster write speeds. As a rule of thumb, 4K-capable recording cameras will usually require at least a U3-rated SD card.

What makes the U1 and U3 memory cards more advanced than those in the Speed Class are that they use one of two UHS bus interfaces:

• UHS-I: theoretical maximum transfer speeds up to 104MB/s
• UHS-II: theoretical maximum transfer speeds up to 312MB/s

Both U1 and U3 memory cards can utilize the UHS-I bus interface but are not compatible with the UHS-II bus interface.

These UHS bus interfaces indicate the theoretical maximum read and write speeds unlike the sustained write speeds of speed classes. The UHS bus interfaces are denoted with a Roman numeral “I” or “II” symbol on the front of the card. The bus speeds refer to the theoretical data transfer rate of the interface itself while a U3-rated SD card has its own sustained write speed of 30MB/s. For example, a UHS-I U3-rated card guarantees a write speed of 30MB/s but has the potential for a read and write speed of up to 104MB/s if used with a device that supports a UHS-I bus interface.

A UHS-II compatible card has a potential read and write speed of up to 312MB/s. The UHS bus interfaces are backwards-compatible so you can use a UHS-II card in a device that supports UHS-I, but you won’t see the speed benefits of UHS-II as the card will default back to the lower specs of UHS-I. Both the card and bus interface must be fully compatible to experience the speed benefits.