Hardware Reference
In-Depth Information
I normally recommend only devices (cameras, PDAs, and so on) that use Secure Digital (SD,
including SD variants like MiniSD or MicroSD), CompactFlash (CF), or USB flash memory. Any of
the others I generally do not recommend due to proprietary designs and higher costs as well as
limitations in capacity and performance.
Secure Digital has become the most popular format in modern devices. It is reasonably fast and is
available in capacities approaching those of CF, and in smaller MiniSD and MicroSD formats, which
are physically compatible with the full-sized SD using adapters. SD sockets also take MMC cards,
which are basically thinner versions of SD. Note that the opposite is not true—MMC sockets do not
accept SD cards.
CF is the most widely used format in professional devices. It offers the highest capacity, in a wide
range of speeds in a reasonably small size.
SD Cards Speed Class and UHS Speed Class Markings
SDHC cards, and some SD and most SDXC cards, are marked with a stylized C icon containing a
number (see Figure 10.3 ) . This is the speed-class marking. Speed class markings include 2, 4, 6, and
10, with 2, 4, and 10 being the most common. Class 2 cards provide sustained read/write speeds of
2MBps or faster, class 4 cards provide sustained read/write speeds of 4MBps or faster, and so on.
Figure 10.3. Speed Class markings on typical SDHC cards.
 
 
 
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