Different Types of SD Cards

Last week, the aged memory card in my phone died, and I had no option to buy a new one, as the warranty period of the last one has ended a long time ago. So I was searching for 'microsd card' on eBay, and I got literally confused which one to buy. Because there seemed to be so many different types of classes of microSD cards, I had to go into R&D mode. After searching on Wikipedia and Nokia Support, I finally made up my mind to buy a class 4 microSD HC card with 16GB memory.

Did you ever wondered why is it called as an SD card ? It stands for 'Secure Digital'. The Secure Digital standard is maintained by the SD Card Association (SDA). It is the most widely implemented memory card format.

The SD cards come in 3 sizes : Standard, Mini and Micro, as shown above. The standard sized cards are mostly used in cameras, while the microSD cards are used as storage memory for smartphones. Those who had used early Nseries models such as N70 and N73, may remember that they used to come with miniSD cards.

The original protocol was defined for cards upto 2GB in size, and they used FAT filesystem. The newer microSD HC a.k.a. High Capacity cards are made using the second version of the protocol, and support file storage upto 32 GB. These are compatible with most of the current handsets.

The manufacturers have even had a further leap miniaturizing the components, and a new breed is entering the market : the SD XC (eXtended Capacity) cards. The format supports a whooping 2TB size support in theory, although only 64 GB and 128 GB cards are currently available. These cards use a newer exFAT file system, thus breaking binary compatibility with older hardware. These cards are expensive too, so please make sure that your phone supports it before buying one.

Apart from the size and capacity ratings, Secure Digital Association rates their memory cards according to data transfer speed, referred to as 'Class'. Both read and write speeds must exceed the specified value. These are defined in terms of suitability for different applications:

• Class 2 for SD video recording
• Class 4 and 6 for HD ~ Full HD video recording,
• Class 10 for Full HD video recording and HD still consecutive recording
• UHS Speed Class 1 for real-time broadcasts and large-size HD videos

The minimum data transfer speed for each class of memory card: (courtesy: Wikipedia)

You need to decide which class of card is suitable for you, as the price goes higher with class. If your use is limited to file management and listening to music, then a class 2 card will be fine for you. However, if your smartphone supports HD video recording, you must buy at least a class 4 card.

The class 10 cards provide no advantage to the current breed of smartphones (some may not even support it), and are only useful if you do a lot of PC to PC transfer. Again, you can get a pen drive with bigger space for that price.

I thought a class 4 microSD HC card with 16 GB memory will suit my needs and bought one at a local store at Rs (₹) 600 (that was cheaper than eBay..!).