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Furthermore, Class A2 cards needs a suitable host driver support to take advantage of their higher speeds, if not their speeds might end up even slower of that of Class A1. The Application Performance Class has two different classes Class A1 and Class A2.Ĭlass A1 requires a minimum of 1500 reading and 500 writing operations per second, whereas Class A2 requires 40 IOPS. IOPS or input/output operations per second is a benchmark to measure the performance of input/output of storage devices such as SD cards, computer hard disk drives and SSDs. Minimum Sequential Write SpeedsĪpplication Performance Class is a recently added standard for SD cards which doesn’t just define sequential reading speeds but also calls for a minimum IOPS for reading and writing.

Video Speed Classīelow is a chart that summarises the SD cards and their speed classes. The symbol for the Video Speed Class has the letter ‘V’ followed by the number that corresponds to the card’s write speed. V6 and V10 can be applied to High Speed and UHS-I cards, while the V30 can be applied to UHS-I cards and the V60 and V90 can be applied to UHS-II and UHS-III cards. V90 – supports minimum write speed of 90MB/sĭue to the similarities in minimum write speeds, the Video Speed Class SD cards can be lumped together with the corresponding UHS Speed Class cards.V60 – supports minimum write speed of 60MB/s.V30 – supports minimum write speed of 30MB/s.V10 – supports minimum write speed of 10MB/s.V6 – supports minimum write speed of 6MB/s.This class of SD cards also different classes that corresponds to their different write speeds which are: Video Speed Class cards also has an important feature to support next generation flash memory such as 3D NAND. This speed class is the most recent addition and is introduced as a response to the demand for high resolution and high quality 4K and 8K video recording.

They are backwards compatible however, so if a device is made with SDXC compatibility then it will be able to support both the SDHC and SD card formats as well. For example, a device that supports SD card formats prior to SDXC cards introduction will only be compatible with the SD and SDHC card formats. Despite that, this isn’t really a “one size fits all” kind of situation as most older devices can’t actually support newer SD card types.