microSDHC Cards For Mobile Devices
Fast memory cards are needed not only in professional equipment like DSLR cameras, but they're increasingly being used in consumer devices like compact cameras, camcorders, MP3 players, hand-held game consoles, and cell phones, too. This accelerating uptake is caused by the rapidly increasing number of features of these devices. The more features, the higher the demands on the memory card. For example, consider recording and playing back HD video on a smartphone. For stutter-free operation, significant data transfer speeds are required. In order to go beyond video snippets a few seconds long, the storage capacity of a memory card also needs to be sufficiently large.
Considering those criteria and adding compatibility, reliability, and robustness, the SD card quickly emerges as the memory card of choice, which also helps to explain its 80% market share.
The physically smallest variant of the SD card is the microSD card, measuring a mere 11 mm x 15 mm x 1 mm (0.43” x 0.59” x 0.04”). Add a host adapter, and a microSD or microSDHC card can be used like a SDHC card.
For this comparison test, we're focusing on the microSDHC subcategory of the microSD form factor, which offers much larger capacities, and thus more versatility in multimedia applications. While a microSD card tops out at 2 GB due to its FAT16 file system, a microSDHC card can store up to 32 GB on its FAT32 file system, depending on the model.
We asked all major memory card manufacturers to submit samples of their microSDHC-based products. We received a wide range of cards, with capacities ranging from 4 GB to 32 GB, and thus covering the whole range of the microSDHC specification. We also noticed plenty of different performance points. SD cards are grouped into several performance classes, which denote the minimum recording rate of the cards. The lowest performance class, Class 2, stores data at a minimum of 2 MB/s. Our test candidates, however, start at performance Class 4, which features a worst-case write speed of 4 MB/s. Class 6 cards achieve at least 6 MB/s, while Class 10 cards switch up the rating a bit, pushing 10 MB/s non-fragmented sequential writes.
