Application Performance Class
These days installing applications and application data to SD memory card is commonly performed as an expanded usage of SD memory card, for example, it is used as workaround in case of a smartphone does not have enough internal memory. The demand of application memory expansion becomes even stronger with the introduction of Android’s Adoptable Storage Device capability. There is a growing need for a combination of random and sequential performance levels improvement.
The Application Performance Class was introduced to realize comfortable application manipulation such as compilation of data which is stored in an SD memory card.
The Application Performance Class 1 (A1) was defined by SD Physical 5.1 specification. Not only for storing maps, pictures, videos, music, dictionary and documents, it also enables user to be freed form sluggish for editing and updating data.
The Application Performance Class 2 (A2) is defined by SD Physical 6.0 specification. It makes SD memory card much higher performance than A1 performance by using functions of Command Queuing and Cache. Efficient flash memory management can be supported by Maintenance functions. Application Performance Class can be applied to UHS SDHC/SDXC Memory Card product family.
The table below describes outline of the Application Performance Class 1 (A1) and Class 2 (A2) specification including Pictograph, the minimum average of random read/write IOPS (IOPS in this case means that the number of 4KB read/write commands can be executed per second), and the minimum sustained sequential performance (MB/s). Those performance requirements are based on measurement under given conditions by the specification.
Host device can identify available Application Performance of card by a field in SD Status register. User can identify available performance by combination of application performance class pictographs. A2 performance is available only the combination of A2 supported host and A2 supported card. At least A1 performance is available by the combination of A1 and A2 pictographs.
You can read more details about the Application Performance Class in our white paper. Watch our video about the Application Performance standard.