If you’ve ever bought a digital camera, or an MP3 player or even a high-end cell phone loaded with features – you’ve inquired, among other things, about the device’s memory. If you’ve noticed, most such hi-tech gadgets don’t have too much in-built memory. However, the retailer will offer to upgrade the memory by inserting what he calls a memory card. At times this memory card is complimentary with the purchase of the device. At other times you will have to pay extra dollars (which you will, because in such a case, the device’s in-built memory will be appalling – dirty little trick, that.) This memory card is known as a secure digital card or an SD card. It is a memory chip, like the one in your computer.

However, an SD card is not be confused with an SDRAM, which is the acronym of Synchronous Dynamic Random Access Memory. The SD was developed and released by three well-known technology biggies – Toshiba, SanDisk and Matsushita – in1999. A secure digital card is a non volatile memory card. Non-volatile memory is memory that remains on any medium (like a CD or a floppy) even when the medium is not powered by the computer or any other device. Data that you store on you flash drive or ROM are examples of non-volatile memory. The SD card is different from other forms of storage because it’s really small and stores relatively large amounts of data and has a security option for writing data on it.

The initial SD cards had a capacity of 2-4 GB. However, high capacity SD cards, known as SDHC cards were eventually created which could hold up to 32 GB of data. Another SD card called the SDXC will be released which will be able to hold data of up to 2 TB. Depending on its size SD cards are classified into SD (24mm*32 mm), miniSD (20 mm*21.5 mm) and micro SD (15mm*11mm). The size, however, does not affect the capacity. SDHC cards are available in all three sizes.

SDHC cards are called secure because of their write-protection option. Most SDHC cards come with a small write protection notch on their left side (not the side with the corner cut off). The presence of this notch makes it impossible to write to the card. An SDHC card must have a sliding tab on this notch for it to be writable. SDHC cards are made very convenient because any portable device and computer can read the card if it is equipped with an SD card reader. The SDHC card can also very easily be formatted from any system if data is ever corrupted and needs to be retrieved.

SDHC cards also have varying speeds, 12 classes of speed actually. However, with technology getting better, newer classes keep emerging and older classes are made redundant. The maximum speed of an SDHC card on the market today is 45Mbps (Megabits per second). This speed is also what makes it desirable to have SDHC memory cards. However, although SD cards are compatible with all devices that have an SD card reader, SDHC cards, at times, are not backward compatible. This means you need to check your reader to see if it can handle cards of above 2GB capacity. Also, the SD slot matters. The smaller sized microSD and miniSD cards are compatible with a large slots but it isn’t the other way round. However, most card readers come with multiple slots to fit every sized SDHC card.

It is also important to understand that SDHC cards are different from your computer’s memory and are used only in portable devices. It would be unwise to leave data on an SD card while it is inserted in your computer like one would in a flash drive. SDHC cards are used in PCs only for transferring data not storing it. However, they are widely used in all other portable devices.

This SDHC Card Review is Written/Updated on Jun 4th, 2009 and filed under Computer Hardware. Both comments and pings are currently closed.

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